Use the conversation messages cache before going online

lib/ui/screens/conversation_screen.dart

@@ -43,7 +43,7 @@ class _ConversationScreenState extends State<ConversationScreen> {
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
-    _loadMessages();
+    _initializeLoading();
   }
 
   void _setError(ErrorLevel err) => setState(() => _error = err);
@@ -55,15 +55,27 @@ class _ConversationScreenState extends State<ConversationScreen> {
     _setError(_messages == null ? ErrorLevel.MAJOR : ErrorLevel.MINOR);
   }
 
+  /// Load the first conversations
+  Future<void> _initializeLoading() async {
+    await _loadMessages(false);
+    await _loadMessages(true);
+  }
+
   /// Load a list of messages
-  Future<void> _loadMessages() async {
+  Future<void> _loadMessages(bool online) async {
     //First, get the messages
     final messages = await _conversationsHelper.getNewMessages(
         conversationID: widget.conversationID,
-        lastMessageID: _messages == null ? 0 : _messages.lastMessageID);
+        lastMessageID: _messages == null ? 0 : _messages.lastMessageID,
+        online: online);
 
     if (messages == null) return _errorLoading();
 
+    // In case we are offline and we did not get any message we do not do
+    // anything (we wait for the online request)
+    if(messages.length == 0 && !online)
+      return;
+
     //Then get information about users
     final usersToGet =
         findMissingFromList(_usersInfo.usersID, messages.getUsersID());
@@ -254,6 +266,9 @@ class _ConversationScreenState extends State<ConversationScreen> {
 
     return Column(
       children: <Widget>[
+        Container(
+          child: _error == ErrorLevel.MINOR ? _buildError() : null,
+        ),
         _buildMessagesList(),
         Divider(),
         _buildSendMessageForm()