Update Kotlin to version 1.7.10

app/ui/base/src/main/java/com/fsck/k9/ui/base/loader/LoaderStateObserver.kt

@@ -33,6 +33,7 @@ private class LoaderStateObserver<T>(
 
     override fun onChanged(state: LoaderState<T>?) {
         when (state) {
+            null -> Unit
             is LoaderState.Loading -> loadingView.show()
             is LoaderState.Error -> errorView.show()
             is LoaderState.Data -> {

app/ui/legacy/src/main/java/com/fsck/k9/activity/MessageList.kt

@@ -124,7 +124,7 @@ open class MessageList :
      * filtered views, e.g. when only displaying the unread messages in a folder.
      */
     private var noThreading = false
-    private var displayMode: DisplayMode? = null
+    private var displayMode: DisplayMode = DisplayMode.MESSAGE_LIST
     private var messageReference: MessageReference? = null
 
     /**
@@ -307,7 +307,7 @@ open class MessageList :
         }
 
         if (savedInstanceState != null) {
-            val savedDisplayMode = savedInstanceState.getSerializable(STATE_DISPLAY_MODE) as DisplayMode?
+            val savedDisplayMode = savedInstanceState.getSerializable(STATE_DISPLAY_MODE) as DisplayMode
             if (savedDisplayMode != DisplayMode.SPLIT_VIEW) {
                 displayMode = savedDisplayMode
                 return

build.gradle

@@ -11,7 +11,7 @@ buildscript {
         ]
 
         versions = [
-                'kotlin': '1.6.10',
+                'kotlin': '1.7.10',
                 'kotlinCoroutines': '1.6.0',
                 'jetbrainsAnnotations': '23.0.0',
                 'androidxAppCompat': '1.4.1',