Notifications: Do not play sound if message has more than one recipient

This prevents Gajim from playing the message_sent sound multiple times

gajim/gui_interface.py

@@ -361,10 +361,13 @@ class Interface:
 
     @staticmethod
     def handle_event_msgsent(obj):
-        #('MSGSENT', account, (jid, msg))
-        # do not play sound when standalone chatstate message (eg no msg)
+        # ('MSGSENT', account, (jid, msg))
+        # Do not play sound if it is a standalone chatstate message (eg no msg)
+        # or if it is a message to more than one recipient
         if obj.message and app.config.get_per('soundevents', 'message_sent',
         'enabled'):
+            if isinstance(obj.jid, list) and len(obj.jid) > 1:
+                return
             helpers.play_sound('message_sent')
 
     @staticmethod