Fix issue #1286 and #844.: when building a query set from filters that reference the same field several times, do not assume each value is a dict

mongoengine/queryset/transform.py

@@ -147,7 +147,7 @@ def query(_doc_cls=None, **kwargs):
         if op is None or key not in mongo_query:
             mongo_query[key] = value
         elif key in mongo_query:
-            if isinstance(mongo_query[key], dict):
+            if isinstance(mongo_query[key], dict) and isinstance(value, dict):
                 mongo_query[key].update(value)
                 # $max/minDistance needs to come last - convert to SON
                 value_dict = mongo_query[key]