try to avoid NPE for currentConversation

On gplay console the following NPE was reported for the line

participantPermissions = ParticipantPermissions(spreedCapabilities, currentConversation!!)

 E  FATAL EXCEPTION: main
          Process: com.nextcloud.talk2, PID: 6626
          java.lang.NullPointerException
          at com.nextcloud.talk.chat.ChatActivity.initObservers$lambda$13(ChatActivity.kt:583)
          at com.nextcloud.talk.chat.ChatActivity.$r8$lambda$QKH5JCFLmCzRMlSJ-EV-m4IW5ig(Unknown Source:0)

which seems that currentConversation was null. If it would have been spreedCapabilities, then the error would have been thrown in the line before..

A reason MAY BE that the observer is triggered before setData on the ViewModel is executed.
While this fix is just not executing code when currentConversation is null, it's unsure if it will follow up problems (like an empty chat) or if the observer is triggered another time when currentConversation is available.

So it's just a hotfix.
To improve the situation in the long term, we should move more logic to viewModel and only use Flow instead to mix it with LiveData.

Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

app/src/main/java/com/nextcloud/talk/chat/ChatActivity.kt

@@ -571,48 +571,63 @@ class ChatActivity :
         chatViewModel.getCapabilitiesViewState.observe(this) { state ->
             when (state) {
                 is ChatViewModel.GetCapabilitiesUpdateState -> {
-                    spreedCapabilities = state.spreedCapabilities
-                    chatApiVersion = ApiUtils.getChatApiVersion(spreedCapabilities, intArrayOf(1))
-                    participantPermissions = ParticipantPermissions(spreedCapabilities, currentConversation!!)
-
-                    invalidateOptionsMenu()
-                    checkShowCallButtons()
-                    checkLobbyState()
-                    updateRoomTimerHandler()
+                    if (currentConversation != null) {
+                        spreedCapabilities = state.spreedCapabilities
+                        chatApiVersion = ApiUtils.getChatApiVersion(spreedCapabilities, intArrayOf(1))
+                        participantPermissions = ParticipantPermissions(spreedCapabilities, currentConversation!!)
+
+                        invalidateOptionsMenu()
+                        checkShowCallButtons()
+                        checkLobbyState()
+                        updateRoomTimerHandler()
+                    } else {
+                        Log.w(
+                            TAG,
+                            "currentConversation was null in observer ChatViewModel.GetCapabilitiesUpdateState"
+                        )
+                    }
                 }
 
                 is ChatViewModel.GetCapabilitiesInitialLoadState -> {
-                    spreedCapabilities = state.spreedCapabilities
-                    chatApiVersion = ApiUtils.getChatApiVersion(spreedCapabilities, intArrayOf(1))
-                    participantPermissions = ParticipantPermissions(spreedCapabilities, currentConversation!!)
-
-                    supportFragmentManager.commit {
-                        setReorderingAllowed(true) // optimizes out redundant replace operations
-                        replace(R.id.fragment_container_activity_chat, messageInputFragment)
-                    }
+                    if (currentConversation != null) {
+                        spreedCapabilities = state.spreedCapabilities
+                        chatApiVersion = ApiUtils.getChatApiVersion(spreedCapabilities, intArrayOf(1))
+                        participantPermissions = ParticipantPermissions(spreedCapabilities, currentConversation!!)
+
+                        supportFragmentManager.commit {
+                            setReorderingAllowed(true) // optimizes out redundant replace operations
+                            replace(R.id.fragment_container_activity_chat, messageInputFragment)
+                        }
 
-                    joinRoomWithPassword()
+                        joinRoomWithPassword()
 
-                    if (conversationUser?.userId != "?" &&
-                        CapabilitiesUtil.hasSpreedFeatureCapability(spreedCapabilities, SpreedFeatures.MENTION_FLAG)
-                    ) {
-                        binding.chatToolbar.setOnClickListener { _ -> showConversationInfoScreen() }
-                    }
+                        if (conversationUser?.userId != "?" &&
+                            CapabilitiesUtil.hasSpreedFeatureCapability(spreedCapabilities, SpreedFeatures.MENTION_FLAG)
+                        ) {
+                            binding.chatToolbar.setOnClickListener { _ -> showConversationInfoScreen() }
+                        }
 
-                    loadAvatarForStatusBar()
-                    setupSwipeToReply()
-                    setActionBarTitle()
+                        loadAvatarForStatusBar()
+                        setupSwipeToReply()
+                        setActionBarTitle()
 
-                    checkShowCallButtons()
-                    checkLobbyState()
-                    updateRoomTimerHandler()
+                        checkShowCallButtons()
+                        checkLobbyState()
+                        updateRoomTimerHandler()
 
-                    val urlForChatting = ApiUtils.getUrlForChat(chatApiVersion, conversationUser?.baseUrl, roomToken)
+                        val urlForChatting =
+                            ApiUtils.getUrlForChat(chatApiVersion, conversationUser?.baseUrl, roomToken)
 
-                    if (adapter?.isEmpty == true) {
-                        chatViewModel.loadMessages(
-                            withCredentials = credentials!!,
-                            withUrl = urlForChatting
+                        if (adapter?.isEmpty == true) {
+                            chatViewModel.loadMessages(
+                                withCredentials = credentials!!,
+                                withUrl = urlForChatting
+                            )
+                        }
+                    } else {
+                        Log.w(
+                            TAG,
+                            "currentConversation was null in observer ChatViewModel.GetCapabilitiesInitialLoadState"
                         )
                     }
                 }