Minor optimization to the database query in send_loop

Author: Jaap Roes

src/mailer/engine.py

@@ -267,7 +267,7 @@ def send_loop():
     """
 
     while True:
-        while not Message.objects.all():
+        while not Message.objects.all().exists():
             logger.debug("sleeping for %s seconds before checking queue again" % EMPTY_QUEUE_SLEEP)
             time.sleep(EMPTY_QUEUE_SLEEP)
         send_all()