Merge pull request #2633 from arthurio/master

Don't use deprecated property for emptiness check

mongoengine/queryset/base.py

@@ -722,7 +722,7 @@ def with_id(self, object_id):
         :param object_id: the value for the id of the document to look up
         """
         queryset = self.clone()
-        if not queryset._query_obj.empty:
+        if queryset._query_obj:
             msg = "Cannot use a filter whilst using `with_id`"
             raise InvalidQueryError(msg)
         return queryset.filter(pk=object_id).first()