Fixed #477: Only re-save session if it's not empty

channels/sessions.py

@@ -70,7 +70,7 @@ def channel_session(func):
             return func(message, *args, **kwargs)
         finally:
             # Persist session if needed
-            if session.modified:
+            if session.modified and not session.is_empty():
                 session.save()
     return inner