Display a notice when there is no messages in a conversation

lib/ui/screens/conversation_screen.dart

@@ -140,7 +140,6 @@ class _ConversationScreenState extends State<ConversationScreen> {
 
   /// Apply new messages [messages] must not be null
   Future<void> _applyNewMessages(ConversationMessagesList messages) async {
-
     // We ignore new messages once the area is no longer visible
     if (!this.mounted) return;
 
@@ -267,6 +266,15 @@ class _ConversationScreenState extends State<ConversationScreen> {
     );
   }
 
+  /// Notice shown when there is no messages to show
+  Widget _buildNoMessagesNotice() {
+    return Expanded(
+      child: Center(
+        child: Text(tr("There is no message yet in this converation.")),
+      ),
+    );
+  }
+
   /// Messages list
   Widget _buildMessagesList() {
     return Expanded(
@@ -372,12 +380,10 @@ class _ConversationScreenState extends State<ConversationScreen> {
               ? _buildLoadingOlderMessage()
               : null,
         ),
-        _buildMessagesList(),
+        _messages.length == 0 ? _buildNoMessagesNotice() : _buildMessagesList(),
         Divider(),
         _buildSendMessageForm()
       ],
     );
   }
-
-
 }