diff --git a/app/src/main/java/ch/dissem/apps/abit/AbstractItemListFragment.kt b/app/src/main/java/ch/dissem/apps/abit/AbstractItemListFragment.kt
index 85ffc16..3907e7d 100644
--- a/app/src/main/java/ch/dissem/apps/abit/AbstractItemListFragment.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/AbstractItemListFragment.kt
@@ -94,9 +94,9 @@ abstract class AbstractItemListFragment<L, T> : ListFragment(), ListHolder<L> {
 
     override fun onSaveInstanceState(outState: Bundle?) {
         super.onSaveInstanceState(outState)
-        if (activatedPosition != ListView.INVALID_POSITION) {
+        if (outState != null && activatedPosition != ListView.INVALID_POSITION) {
             // Serialize and persist the activated item position.
-            outState!!.putInt(STATE_ACTIVATED_POSITION, activatedPosition)
+            outState.putInt(STATE_ACTIVATED_POSITION, activatedPosition)
         }
     }
 
diff --git a/app/src/main/java/ch/dissem/apps/abit/AddressListFragment.kt b/app/src/main/java/ch/dissem/apps/abit/AddressListFragment.kt
index c34cbee..abd52fc 100644
--- a/app/src/main/java/ch/dissem/apps/abit/AddressListFragment.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/AddressListFragment.kt
@@ -68,11 +68,12 @@ class AddressListFragment : AbstractItemListFragment<Void, BitmessageAddress>()
                     v = convertView.tag as ViewHolder
                     result = convertView
                 }
-                val item = getItem(position)!!
-                v.avatar.setImageDrawable(Identicon(item))
-                v.name.text = item.toString()
-                v.streamNumber.text = v.ctx.getString(R.string.stream_number, item.stream)
-                v.subscribed.visibility = if (item.isSubscribed) View.VISIBLE else View.INVISIBLE
+                getItem(position)?.let { item ->
+                    v.avatar.setImageDrawable(Identicon(item))
+                    v.name.text = item.toString()
+                    v.streamNumber.text = v.ctx.getString(R.string.stream_number, item.stream)
+                    v.subscribed.visibility = if (item.isSubscribed) View.VISIBLE else View.INVISIBLE
+                }
                 return result
             }
         }
diff --git a/app/src/main/java/ch/dissem/apps/abit/ComposeMessageActivity.kt b/app/src/main/java/ch/dissem/apps/abit/ComposeMessageActivity.kt
index 49e0bcd..39310d2 100644
--- a/app/src/main/java/ch/dissem/apps/abit/ComposeMessageActivity.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/ComposeMessageActivity.kt
@@ -37,14 +37,17 @@ class ComposeMessageActivity : AppCompatActivity() {
         setContentView(R.layout.toolbar_layout)
 
         setSupportActionBar(toolbar)
-        supportActionBar!!.setHomeAsUpIndicator(R.drawable.ic_action_close)
-        supportActionBar!!.setDisplayHomeAsUpEnabled(true)
-        supportActionBar!!.setHomeButtonEnabled(false)
+        supportActionBar?.apply {
+            setHomeAsUpIndicator(R.drawable.ic_action_close)
+            setDisplayHomeAsUpEnabled(true)
+            setHomeButtonEnabled(false)
+        }
 
         // Display the fragment as the main content.
         val fragment = ComposeMessageFragment()
         fragment.arguments = intent.extras
-        supportFragmentManager.beginTransaction()
+        supportFragmentManager
+                .beginTransaction()
                 .replace(R.id.content, fragment)
                 .commit()
     }
@@ -69,7 +72,7 @@ class ComposeMessageActivity : AppCompatActivity() {
         private fun getReplyIntent(ctx: Context, item: Plaintext): Intent {
             val replyIntent = Intent(ctx, ComposeMessageActivity::class.java)
             val receivingIdentity = item.to
-            if (receivingIdentity!!.isChan) {
+            if (receivingIdentity?.isChan ?: false) {
                 // reply to chan, not to the sender of the message
                 replyIntent.putExtra(EXTRA_RECIPIENT, receivingIdentity)
                 // I hate when people send as chan, so it won't be the default behaviour.
@@ -84,14 +87,14 @@ class ComposeMessageActivity : AppCompatActivity() {
                 replyIntent.putExtra(EXTRA_ENCODING, EXTENDED)
             }
             replyIntent.putExtra(EXTRA_PARENT, item)
-            val prefix: String
-            if (item.subject!!.length >= 3 && item.subject!!.substring(0, 3)
-                    .equals("RE:", ignoreCase = true)) {
-                prefix = ""
-            } else {
-                prefix = "RE: "
+            item.subject?.let { subject ->
+                val prefix: String = if (subject.length >= 3 && subject.substring(0, 3).equals("RE:", ignoreCase = true)) {
+                    ""
+                } else {
+                    "RE: "
+                }
+                replyIntent.putExtra(EXTRA_SUBJECT, prefix + subject)
             }
-            replyIntent.putExtra(EXTRA_SUBJECT, prefix + item.subject!!)
             replyIntent.putExtra(EXTRA_CONTENT,
                     "\n\n------------------------------------------------------\n" + item.text!!)
             return replyIntent
diff --git a/app/src/main/java/ch/dissem/apps/abit/DetailActivity.kt b/app/src/main/java/ch/dissem/apps/abit/DetailActivity.kt
index b6ae31b..2890b01 100644
--- a/app/src/main/java/ch/dissem/apps/abit/DetailActivity.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/DetailActivity.kt
@@ -19,7 +19,9 @@ abstract class DetailActivity : AppCompatActivity() {
 
         setSupportActionBar(toolbar)
         // Show the Up button in the action bar.
-        supportActionBar!!.setDisplayHomeAsUpEnabled(true)
+        supportActionBar?.apply {
+            setDisplayHomeAsUpEnabled(true)
+        }
 
         MaterializeBuilder()
                 .withActivity(this)
diff --git a/app/src/main/java/ch/dissem/apps/abit/MessageDetailFragment.kt b/app/src/main/java/ch/dissem/apps/abit/MessageDetailFragment.kt
index bcfa9cf..51a1bdd 100644
--- a/app/src/main/java/ch/dissem/apps/abit/MessageDetailFragment.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/MessageDetailFragment.kt
@@ -145,8 +145,8 @@ class MessageDetailFragment : Fragment() {
         recyclerView.layoutManager = LinearLayoutManager(activity)
     }
 
-    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater?) {
-        inflater!!.inflate(R.menu.message, menu)
+    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
+        inflater.inflate(R.menu.message, menu)
 
         Drawables.addIcon(activity, menu, R.id.reply, GoogleMaterial.Icon.gmd_reply)
         Drawables.addIcon(activity, menu, R.id.delete, GoogleMaterial.Icon.gmd_delete)
diff --git a/app/src/main/java/ch/dissem/apps/abit/MessageListFragment.kt b/app/src/main/java/ch/dissem/apps/abit/MessageListFragment.kt
index 7cde336..9974878 100644
--- a/app/src/main/java/ch/dissem/apps/abit/MessageListFragment.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/MessageListFragment.kt
@@ -90,7 +90,7 @@ class MessageListFragment : Fragment(), ListHolder<Label> {
     }
 
     override fun updateList(label: Label) {
-        if (currentLabel != null && currentLabel != label && currentLabel != backStack.peek()) {
+        if (currentLabel != null && currentLabel != label && (backStack.isEmpty() || currentLabel != backStack.peek())) {
             backStack.push(currentLabel)
         }
         if (!isResumed) {
diff --git a/app/src/main/java/ch/dissem/apps/abit/StatusActivity.kt b/app/src/main/java/ch/dissem/apps/abit/StatusActivity.kt
index cd92978..6a56e82 100644
--- a/app/src/main/java/ch/dissem/apps/abit/StatusActivity.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/StatusActivity.kt
@@ -30,8 +30,10 @@ class StatusActivity : AppCompatActivity() {
         setContentView(R.layout.activity_status)
 
         setSupportActionBar(toolbar)
-        supportActionBar!!.setDisplayHomeAsUpEnabled(true)
-        supportActionBar!!.setHomeButtonEnabled(false)
+        supportActionBar?.apply {
+            setDisplayHomeAsUpEnabled(true)
+            setHomeButtonEnabled(false)
+        }
 
         MaterializeBuilder()
                 .withActivity(this)
diff --git a/app/src/main/java/ch/dissem/apps/abit/adapter/ContactAdapter.kt b/app/src/main/java/ch/dissem/apps/abit/adapter/ContactAdapter.kt
index cc8458f..fe05c12 100644
--- a/app/src/main/java/ch/dissem/apps/abit/adapter/ContactAdapter.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/adapter/ContactAdapter.kt
@@ -83,31 +83,28 @@ class ContactAdapter(ctx: Context) : BaseAdapter(), Filterable {
 
                 val newValues = ArrayList<BitmessageAddress>()
 
-                for (i in originalData.indices) {
-                    val value = originalData[i]
-
-                    // First match against the whole, non-splitted value
-                    if (value.alias != null) {
-                        val alias = value.alias!!.toLowerCase()
-                        if (alias.startsWith(prefixString)) {
-                            newValues.add(value)
-                        } else {
-                            val words = alias.split(" ".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
-
-                            for (word in words) {
-                                if (word.startsWith(prefixString)) {
+                originalData
+                        .forEach { value ->
+                            value.alias?.toLowerCase()?.let { alias ->
+                                if (alias.startsWith(prefixString)) {
                                     newValues.add(value)
-                                    break
+                                } else {
+                                    val words = alias.split(" ".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
+
+                                    for (word in words) {
+                                        if (word.startsWith(prefixString)) {
+                                            newValues.add(value)
+                                            break
+                                        }
+                                    }
                                 }
-                            }
+                            } ?: {
+                                val address = value.address.toLowerCase()
+                                if (address.contains(prefixString)) {
+                                    newValues.add(value)
+                                }
+                            }.invoke()
                         }
-                    } else {
-                        val address = value.address.toLowerCase()
-                        if (address.contains(prefixString)) {
-                            newValues.add(value)
-                        }
-                    }
-                }
 
                 results.values = newValues
                 results.count = newValues.size
diff --git a/app/src/main/java/ch/dissem/apps/abit/dialog/DeterministicIdentityDialogFragment.kt b/app/src/main/java/ch/dissem/apps/abit/dialog/DeterministicIdentityDialogFragment.kt
index 22d1988..db29902 100644
--- a/app/src/main/java/ch/dissem/apps/abit/dialog/DeterministicIdentityDialogFragment.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/dialog/DeterministicIdentityDialogFragment.kt
@@ -32,7 +32,6 @@ import ch.dissem.bitmessage.entity.payload.Pubkey
 import kotlinx.android.synthetic.main.dialog_add_deterministic_identity.*
 import org.jetbrains.anko.doAsync
 import org.jetbrains.anko.uiThread
-import kotlinx.android.synthetic.main.dialog_add_deterministic_identity.*
 
 /**
  * @author Christian Basler
@@ -50,19 +49,17 @@ class DeterministicIdentityDialogFragment : AppCompatDialogFragment() {
         return inflater.inflate(R.layout.dialog_add_deterministic_identity, container, false)
     }
 
-    override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
-        super.onViewCreated(view, savedInstanceState)
+    override fun onViewCreated(dialogView: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(dialogView, savedInstanceState)
         ok.setOnClickListener {
             dismiss()
             val context = activity.baseContext
-            val dialogView = getView()!!
-            val passphrase = dialogView.findViewById(R.id.passphrase) as TextView
+            val passphraseText = passphrase.text.toString()
 
-            Toast.makeText(context, R.string.toast_long_running_operation,
-                    Toast.LENGTH_SHORT).show()
+            Toast.makeText(context, R.string.toast_long_running_operation, Toast.LENGTH_SHORT).show()
             doAsync {
                 val identities = bmc.createDeterministicAddresses(
-                        passphrase.text.toString(),
+                        passphraseText,
                         number_of_identities.text.toString().toInt(),
                         Pubkey.LATEST_VERSION,
                         1L,
diff --git a/app/src/main/java/ch/dissem/apps/abit/notification/NetworkNotification.kt b/app/src/main/java/ch/dissem/apps/abit/notification/NetworkNotification.kt
index 0e268a7..8a22db0 100644
--- a/app/src/main/java/ch/dissem/apps/abit/notification/NetworkNotification.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/notification/NetworkNotification.kt
@@ -41,11 +41,11 @@ class NetworkNotification(ctx: Context) : AbstractNotification(ctx) {
         val showAppIntent = Intent(ctx, MainActivity::class.java)
         val pendingIntent = PendingIntent.getActivity(ctx, 1, showAppIntent, 0)
         builder
-            .setSmallIcon(R.drawable.ic_notification_full_node)
-            .setContentTitle(ctx.getString(R.string.bitmessage_full_node))
-            .setVisibility(NotificationCompat.VISIBILITY_PUBLIC)
-            .setShowWhen(false)
-            .setContentIntent(pendingIntent)
+                .setSmallIcon(R.drawable.ic_notification_full_node)
+                .setContentTitle(ctx.getString(R.string.bitmessage_full_node))
+                .setVisibility(NotificationCompat.VISIBILITY_PUBLIC)
+                .setShowWhen(false)
+                .setContentIntent(pendingIntent)
     }
 
     @SuppressLint("StringFormatMatches")
@@ -55,7 +55,7 @@ class NetworkNotification(ctx: Context) : AbstractNotification(ctx) {
         val connections = BitmessageService.status.getProperty("network", "connections")
         if (!running) {
             builder.setContentText(ctx.getString(R.string.connection_info_disconnected))
-        } else if (connections!!.properties.isEmpty()) {
+        } else if (connections == null || connections.properties.isEmpty()) {
             builder.setContentText(ctx.getString(R.string.connection_info_pending))
         } else {
             val info = StringBuilder()
@@ -64,10 +64,10 @@ class NetworkNotification(ctx: Context) : AbstractNotification(ctx) {
                 val nodeCount = stream.getProperty("nodes")!!.value as Int?
                 if (nodeCount == 1) {
                     info.append(ctx.getString(R.string.connection_info_1,
-                        streamNumber))
+                            streamNumber))
                 } else {
                     info.append(ctx.getString(R.string.connection_info_n,
-                        streamNumber, nodeCount))
+                            streamNumber, nodeCount))
                 }
                 info.append('\n')
             }
@@ -78,13 +78,13 @@ class NetworkNotification(ctx: Context) : AbstractNotification(ctx) {
         if (running) {
             intent.putExtra(BitmessageIntentService.EXTRA_SHUTDOWN_NODE, true)
             builder.addAction(R.drawable.ic_notification_node_stop,
-                ctx.getString(R.string.full_node_stop),
-                PendingIntent.getService(ctx, 0, intent, FLAG_UPDATE_CURRENT))
+                    ctx.getString(R.string.full_node_stop),
+                    PendingIntent.getService(ctx, 0, intent, FLAG_UPDATE_CURRENT))
         } else {
             intent.putExtra(BitmessageIntentService.EXTRA_STARTUP_NODE, true)
             builder.addAction(R.drawable.ic_notification_node_start,
-                ctx.getString(R.string.full_node_restart),
-                PendingIntent.getService(ctx, 1, intent, FLAG_UPDATE_CURRENT))
+                    ctx.getString(R.string.full_node_restart),
+                    PendingIntent.getService(ctx, 1, intent, FLAG_UPDATE_CURRENT))
         }
         notification = builder.build()
         return running
@@ -117,8 +117,8 @@ class NetworkNotification(ctx: Context) : AbstractNotification(ctx) {
         intent.putExtra(BitmessageIntentService.EXTRA_SHUTDOWN_NODE, true)
         builder.mActions.clear()
         builder.addAction(R.drawable.ic_notification_node_stop,
-            ctx.getString(R.string.full_node_stop),
-            PendingIntent.getService(ctx, 0, intent, FLAG_UPDATE_CURRENT))
+                ctx.getString(R.string.full_node_stop),
+                PendingIntent.getService(ctx, 0, intent, FLAG_UPDATE_CURRENT))
         notification = builder.build()
     }
 
diff --git a/app/src/main/java/ch/dissem/apps/abit/notification/NewMessageNotification.kt b/app/src/main/java/ch/dissem/apps/abit/notification/NewMessageNotification.kt
index 0951851..853a45f 100644
--- a/app/src/main/java/ch/dissem/apps/abit/notification/NewMessageNotification.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/notification/NewMessageNotification.kt
@@ -45,8 +45,9 @@ class NewMessageNotification(ctx: Context) : AbstractNotification(ctx) {
     fun singleNotification(plaintext: Plaintext): NewMessageNotification {
         val builder = NotificationCompat.Builder(ctx)
         val bigText = SpannableString(plaintext.subject + "\n" + plaintext.text)
-        bigText.setSpan(SPAN_EMPHASIS, 0, plaintext.subject!!.length, Spanned
-                .SPAN_INCLUSIVE_EXCLUSIVE)
+        plaintext.subject?.let { subject ->
+            bigText.setSpan(SPAN_EMPHASIS, 0, subject.length, Spanned.SPAN_INCLUSIVE_EXCLUSIVE)
+        }
         builder.setSmallIcon(R.drawable.ic_notification_new_message)
                 .setLargeIcon(toBitmap(Identicon(plaintext.from), 192))
                 .setContentTitle(plaintext.from.toString())
diff --git a/app/src/main/java/ch/dissem/apps/abit/repository/AndroidMessageRepository.kt b/app/src/main/java/ch/dissem/apps/abit/repository/AndroidMessageRepository.kt
index 6c9164e..963393b 100644
--- a/app/src/main/java/ch/dissem/apps/abit/repository/AndroidMessageRepository.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/repository/AndroidMessageRepository.kt
@@ -161,11 +161,12 @@ class AndroidMessageRepository(private val sql: SqlHelper, private val context:
 
 
     private fun updateParents(db: SQLiteDatabase, message: Plaintext) {
-        if (message.inventoryVector == null || message.parents.isEmpty()) {
+        val inventoryVector = message.inventoryVector
+        if (inventoryVector == null || message.parents.isEmpty()) {
             // There are no parents to save yet (they are saved in the extended data, that's enough for now)
             return
         }
-        val childIV = message.inventoryVector!!.hash
+        val childIV = inventoryVector.hash
         db.delete(PARENTS_TABLE_NAME, "child=?", arrayOf(hex(childIV)))
 
         // save new parents
@@ -347,7 +348,7 @@ class AndroidMessageRepository(private val sql: SqlHelper, private val context:
 
     override fun remove(message: Plaintext) {
         val db = sql.writableDatabase
-        db.delete(TABLE_NAME, "id = " + message.id!!, null)
+        db.delete(TABLE_NAME, "id = ?", arrayOf(message.id.toString()))
     }
 
     companion object {
diff --git a/app/src/main/java/ch/dissem/apps/abit/repository/SqlHelper.kt b/app/src/main/java/ch/dissem/apps/abit/repository/SqlHelper.kt
index c536000..6a21a02 100644
--- a/app/src/main/java/ch/dissem/apps/abit/repository/SqlHelper.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/repository/SqlHelper.kt
@@ -97,7 +97,7 @@ class SqlHelper(private val ctx: Context) : SQLiteOpenHelper(ctx, DATABASE_NAME,
     companion object {
         // If you change the database schema, you must increment the database version.
         private val DATABASE_VERSION = 7
-        private val DATABASE_NAME = "jabit.db"
+        val DATABASE_NAME = "jabit.db"
 
         internal fun join(vararg types: Enum<*>): String = types.joinToString(separator = "', '", prefix = "'", postfix = "'", transform = {it.name})
     }
diff --git a/app/src/main/java/ch/dissem/apps/abit/service/BitmessageIntentService.kt b/app/src/main/java/ch/dissem/apps/abit/service/BitmessageIntentService.kt
index 2b656e5..7156ce9 100644
--- a/app/src/main/java/ch/dissem/apps/abit/service/BitmessageIntentService.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/service/BitmessageIntentService.kt
@@ -36,17 +36,19 @@ class BitmessageIntentService : IntentService("BitmessageIntentService") {
     }
 
     override fun onHandleIntent(intent: Intent?) {
-        if (intent!!.hasExtra(EXTRA_DELETE_MESSAGE)) {
-            val item = intent.getSerializableExtra(EXTRA_DELETE_MESSAGE) as Plaintext
-            bmc.labeler.delete(item)
-            bmc.messages.save(item)
-            Singleton.getMessageListener(this).resetNotification()
-        }
-        if (intent.hasExtra(EXTRA_STARTUP_NODE)) {
-            NetworkUtils.enableNode(this)
-        }
-        if (intent.hasExtra(EXTRA_SHUTDOWN_NODE)) {
-            NetworkUtils.disableNode(this)
+        intent?.let {
+            if (it.hasExtra(EXTRA_DELETE_MESSAGE)) {
+                val item = it.getSerializableExtra(EXTRA_DELETE_MESSAGE) as Plaintext
+                bmc.labeler.delete(item)
+                bmc.messages.save(item)
+                Singleton.getMessageListener(this).resetNotification()
+            }
+            if (it.hasExtra(EXTRA_STARTUP_NODE)) {
+                NetworkUtils.enableNode(this)
+            }
+            if (it.hasExtra(EXTRA_SHUTDOWN_NODE)) {
+                NetworkUtils.disableNode(this)
+            }
         }
     }
 
diff --git a/app/src/main/java/ch/dissem/apps/abit/service/ServicePowEngine.kt b/app/src/main/java/ch/dissem/apps/abit/service/ServicePowEngine.kt
index 848ee91..da0dc4e 100644
--- a/app/src/main/java/ch/dissem/apps/abit/service/ServicePowEngine.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/service/ServicePowEngine.kt
@@ -42,7 +42,7 @@ class ServicePowEngine(private val ctx: Context) : ProofOfWorkEngine {
             synchronized(lock) {
                 this@ServicePowEngine.service = service as PowBinder
                 while (!queue.isEmpty()) {
-                    this@ServicePowEngine.service!!.process(queue.poll())
+                    service.process(queue.poll())
                 }
             }
         }
@@ -57,8 +57,7 @@ class ServicePowEngine(private val ctx: Context) : ProofOfWorkEngine {
         synchronized(lock) {
             service?.process(item) ?: {
                 queue.add(item)
-                ctx.bindService(Intent(ctx, ProofOfWorkService::class.java), connection,
-                        BIND_AUTO_CREATE)
+                ctx.bindService(Intent(ctx, ProofOfWorkService::class.java), connection, BIND_AUTO_CREATE)
             }.invoke()
         }
     }
diff --git a/app/src/main/java/ch/dissem/apps/abit/service/Singleton.kt b/app/src/main/java/ch/dissem/apps/abit/service/Singleton.kt
index b79a379..395902a 100644
--- a/app/src/main/java/ch/dissem/apps/abit/service/Singleton.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/service/Singleton.kt
@@ -30,7 +30,6 @@ import ch.dissem.bitmessage.BitmessageContext
 import ch.dissem.bitmessage.entity.BitmessageAddress
 import ch.dissem.bitmessage.entity.payload.Pubkey
 import ch.dissem.bitmessage.networking.nio.NioNetworkHandler
-import ch.dissem.bitmessage.ports.ProofOfWorkRepository
 import ch.dissem.bitmessage.utils.ConversationService
 import ch.dissem.bitmessage.utils.TTL
 import ch.dissem.bitmessage.utils.UnixTime.DAY
@@ -53,7 +52,8 @@ object Singleton {
         return init({ bitmessageContext }, { bitmessageContext = it }) {
             val ctx = context.applicationContext
             val sqlHelper = SqlHelper(ctx)
-            powRepo = AndroidProofOfWorkRepository(sqlHelper)
+            val powRepo = AndroidProofOfWorkRepository(sqlHelper)
+            this.powRepo = powRepo
             TTL.pubkey = 2 * DAY
             BitmessageContext.Builder()
                     .proofOfWorkEngine(SwitchingProofOfWorkEngine(
@@ -66,7 +66,7 @@ object Singleton {
                     .inventory(AndroidInventory(sqlHelper))
                     .addressRepo(AndroidAddressRepository(sqlHelper))
                     .messageRepo(AndroidMessageRepository(sqlHelper, ctx))
-                    .powRepo(powRepo!!)
+                    .powRepo(powRepo)
                     .networkHandler(NioNetworkHandler())
                     .listener(getMessageListener(ctx))
                     .doNotSendPubkeyOnIdentityCreation()
@@ -80,10 +80,7 @@ object Singleton {
 
     fun getAddressRepository(ctx: Context) = getBitmessageContext(ctx).addresses as AndroidAddressRepository
 
-    fun getProofOfWorkRepository(ctx: Context): ProofOfWorkRepository {
-        if (powRepo == null) getBitmessageContext(ctx)
-        return powRepo!!
-    }
+    fun getProofOfWorkRepository(ctx: Context) = powRepo ?: getBitmessageContext(ctx).internals.proofOfWorkRepository
 
     fun getIdentity(ctx: Context): BitmessageAddress? {
         return init<BitmessageAddress?>(ctx, { identity }, { identity = it }) { bmc ->
diff --git a/app/src/main/java/ch/dissem/apps/abit/synchronization/SyncAdapter.kt b/app/src/main/java/ch/dissem/apps/abit/synchronization/SyncAdapter.kt
index 63f3903..e7c1c84 100644
--- a/app/src/main/java/ch/dissem/apps/abit/synchronization/SyncAdapter.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/synchronization/SyncAdapter.kt
@@ -104,7 +104,7 @@ class SyncAdapter(context: Context, autoInitialize: Boolean) : AbstractThreadedS
         // If the Bitmessage context acts as a full node, synchronization isn't necessary
         LOG.info("Looking for completed POW")
 
-        val privateKey = identity.privateKey!!.privateEncryptionKey
+        val privateKey = identity.privateKey?.privateEncryptionKey ?: throw IllegalStateException("Identity without private key")
         val signingKey = cryptography().createPublicKey(identity.publicDecryptionKey)
         val reader = ProofOfWorkRequest.Reader(identity)
         val powRepo = Singleton.getProofOfWorkRepository(context)
diff --git a/app/src/main/java/ch/dissem/apps/abit/util/Drawables.kt b/app/src/main/java/ch/dissem/apps/abit/util/Drawables.kt
index 6639d14..a7c26e8 100644
--- a/app/src/main/java/ch/dissem/apps/abit/util/Drawables.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/util/Drawables.kt
@@ -70,11 +70,12 @@ object Drawables {
         if (address.alias != null) {
             link.append("?label=").append(address.alias)
         }
-        if (address.pubkey != null) {
+        address.pubkey?.apply {
             link.append(if (address.alias == null) '?' else '&')
             val pubkey = ByteArrayOutputStream()
-            address.pubkey!!.writeUnencrypted(pubkey)
+            writeUnencrypted(pubkey)
             link.append("pubkey=").append(Base64.encodeToString(pubkey.toByteArray(), URL_SAFE or NO_WRAP))
+
         }
         val result: BitMatrix
         try {
diff --git a/app/src/main/java/ch/dissem/apps/abit/util/PowStats.kt b/app/src/main/java/ch/dissem/apps/abit/util/PowStats.kt
index 65d93c5..9933cfc 100644
--- a/app/src/main/java/ch/dissem/apps/abit/util/PowStats.kt
+++ b/app/src/main/java/ch/dissem/apps/abit/util/PowStats.kt
@@ -10,7 +10,7 @@ import java.math.BigInteger
  * POW statistics that might help estimate the POW time, depending on
  */
 object PowStats {
-    private val TWO_POW_64 = BigInteger.valueOf(2).pow(64)!!
+    private val TWO_POW_64: BigInteger = BigInteger.valueOf(2).pow(64)
 
     var averagePowUnitTime = 0L
     var powCount = 0L