wire up message loading

src/message-list/message-list-model.vala

@@ -3,6 +3,8 @@ using Gee;
 
 public class MessageListModel : Object, ListModel 
 {
+    public signal void messages_changed();
+
     public SortedSet<Message> messages {
         owned get { return _messages.read_only_view; }
     }
@@ -49,6 +51,8 @@ public class MessageListModel : Object, ListModel
         } catch (Error e) {
             warning("Failed to load messages: %s", e.message);
         }
+
+        messages_changed();
     }
 
     private void got_messages_updated(string conversation_guid) {