Fix crash when the message list is empty when recovering from a network loss

app/src/main/java/chat/rocket/android/chatroom/presentation/ChatRoomPresenter.kt

@@ -188,7 +188,8 @@ class ChatRoomPresenter @Inject constructor(private val view: ChatRoomView,
         launch(parent = strategy.jobs) {
             if (chatRoomId != null && chatRoomType != null) {
                 val roomType = roomTypeOf(chatRoomType!!)
-                val lastMessage = messagesRepository.getByRoomId(chatRoomId!!).sortedByDescending { it.timestamp }.first()
+                messagesRepository.getByRoomId(chatRoomId!!)
+                        .sortedByDescending { it.timestamp }.firstOrNull()?.let { lastMessage ->
                             val instant = Instant.ofEpochMilli(lastMessage.timestamp)
                             val messages = client.history(chatRoomId!!, roomType, count = 50,
                                     oldest = instant.toString())
@@ -210,6 +211,7 @@ class ChatRoomPresenter @Inject constructor(private val view: ChatRoomView,
                         }
             }
         }
+    }
 
     fun unsubscribeMessages(chatRoomId: String) {
         manager.removeStatusChannel(stateChannel)