[Audio] Fix trying to send notify message with no channel object (#6429)

redbot/cogs/audio/core/events/cog.py

@@ -198,6 +198,8 @@ class AudioEvents(MixinMeta, metaclass=CompositeMetaClass):
         if not guild:
             return
         notify_channel = guild.get_channel_or_thread(player.fetch("notify_channel"))
+        if not notify_channel:
+            return
         has_perms = self._has_notify_perms(notify_channel)
         tries = 0
         while not player._is_playing: