diff --git a/app/ui/legacy/src/main/java/com/fsck/k9/activity/MessageList.kt b/app/ui/legacy/src/main/java/com/fsck/k9/activity/MessageList.kt
index 714d8b20ae1c61649a9b1166ab0b3e599f06f1e0..a4a112975425eaff46be35ef1dcff81305eef106 100644
--- a/app/ui/legacy/src/main/java/com/fsck/k9/activity/MessageList.kt
+++ b/app/ui/legacy/src/main/java/com/fsck/k9/activity/MessageList.kt
@@ -661,7 +661,7 @@ open class MessageList :
         openFolderTransaction!!.commit()
         openFolderTransaction = null
 
-        messageListFragment!!.setFullyActive()
+        messageListFragment?.setFullyActive()
 
         onMessageListDisplayed()
     }
@@ -807,15 +807,15 @@ open class MessageList :
 
         when (if (event.unicodeChar != 0) event.unicodeChar.toChar() else null) {
             'c' -> {
-                messageListFragment!!.onCompose()
+                messageListFragment?.onCompose()
                 return true
             }
             'o' -> {
-                messageListFragment!!.onCycleSort()
+                messageListFragment?.onCycleSort()
                 return true
             }
             'i' -> {
-                messageListFragment!!.onReverseSort()
+                messageListFragment?.onReverseSort()
                 return true
             }
             'd' -> {
@@ -823,12 +823,12 @@ open class MessageList :
                 return true
             }
             's' -> {
-                messageListFragment!!.toggleMessageSelect()
+                messageListFragment?.toggleMessageSelect()
                 return true
             }
             'g' -> {
                 if (displayMode == DisplayMode.MESSAGE_LIST) {
-                    messageListFragment!!.onToggleFlagged()
+                    messageListFragment?.onToggleFlagged()
                 } else if (messageViewContainerFragment != null) {
                     messageViewContainerFragment!!.onToggleFlagged()
                 }
@@ -836,7 +836,7 @@ open class MessageList :
             }
             'm' -> {
                 if (displayMode == DisplayMode.MESSAGE_LIST) {
-                    messageListFragment!!.onMove()
+                    messageListFragment?.onMove()
                 } else if (messageViewContainerFragment != null) {
                     messageViewContainerFragment!!.onMove()
                 }
@@ -844,7 +844,7 @@ open class MessageList :
             }
             'v' -> {
                 if (displayMode == DisplayMode.MESSAGE_LIST) {
-                    messageListFragment!!.onArchive()
+                    messageListFragment?.onArchive()
                 } else if (messageViewContainerFragment != null) {
                     messageViewContainerFragment!!.onArchive()
                 }
@@ -852,7 +852,7 @@ open class MessageList :
             }
             'y' -> {
                 if (displayMode == DisplayMode.MESSAGE_LIST) {
-                    messageListFragment!!.onCopy()
+                    messageListFragment?.onCopy()
                 } else if (messageViewContainerFragment != null) {
                     messageViewContainerFragment!!.onCopy()
                 }
@@ -860,7 +860,7 @@ open class MessageList :
             }
             'z' -> {
                 if (displayMode == DisplayMode.MESSAGE_LIST) {
-                    messageListFragment!!.onToggleRead()
+                    messageListFragment?.onToggleRead()
                 } else if (messageViewContainerFragment != null) {
                     messageViewContainerFragment!!.onToggleRead()
                 }
@@ -903,7 +903,7 @@ open class MessageList :
 
     private fun onDeleteHotKey() {
         if (displayMode == DisplayMode.MESSAGE_LIST) {
-            messageListFragment!!.onDelete()
+            messageListFragment?.onDelete()
         } else if (messageViewContainerFragment != null) {
             messageViewContainerFragment!!.onDelete()
         }
@@ -1158,7 +1158,7 @@ open class MessageList :
             fragmentTransaction.commit()
         }
 
-        messageListFragment!!.setActiveMessage(null)
+        messageListFragment?.setActiveMessage(null)
     }
 
     private fun removeMessageViewContainerFragment() {
@@ -1173,10 +1173,12 @@ open class MessageList :
     }
 
     private fun removeMessageListFragment() {
-        val fragmentTransaction = supportFragmentManager.beginTransaction()
-        fragmentTransaction.remove(messageListFragment!!)
-        messageListFragment = null
-        fragmentTransaction.commit()
+        messageListFragment?.let {
+            val fragmentTransaction = supportFragmentManager.beginTransaction()
+            fragmentTransaction.remove(it)
+            messageListFragment = null
+            fragmentTransaction.commit()
+        }
     }
 
     override fun goBack() {
@@ -1247,8 +1249,8 @@ open class MessageList :
         displayMode = DisplayMode.MESSAGE_LIST
 
         messageViewContainerFragment?.isActive = false
-        messageListFragment!!.isActive = true
-        messageListFragment!!.setActiveMessage(null)
+        messageListFragment?.isActive = true
+        messageListFragment?.setActiveMessage(null)
 
         viewSwitcher!!.showFirstView()
 
@@ -1289,9 +1291,7 @@ open class MessageList :
     }
 
     private fun showDefaultTitleView() {
-        if (messageListFragment != null) {
-            messageListFragment!!.updateTitle()
-        }
+        messageListFragment?.updateTitle()
     }
 
     private fun showMessageTitleView() {