fix crash upon receiving empty inbounds

marznode/service/service.py

@@ -70,11 +70,14 @@ async def _update_user(self, user_data: UserData):
             )
             return
         elif not user_data.inbounds and storage_user:
-            """remove in case we have th user but client has sent
+            """remove in case we have the user but client has sent
             us an empty list of inbounds"""
             await self._remove_user(storage_user, storage_user.inbounds)
             return await self._storage.remove_user(user)
-
+        elif not user_data.inbounds and not storage_user:
+            """we're asked to remove a user which we don't have, just pass."""
+            return
+
         """otherwise synchronize the user with what 
         the client has sent us"""
         storage_tags = {i.tag for i in storage_user.inbounds}