skip dumps/loads dance unless encoder is specified

Author: timgraham

django_mongodb/operations.py

@@ -52,6 +52,8 @@ def adapt_decimalfield_value(self, value, max_digits=None, decimal_places=None):
         return Decimal128(value)
 
     def adapt_json_value(self, value, encoder):
+        if not encoder:
+            return value
         try:
             return json.loads(json.dumps(value, cls=encoder))
         except json.decoder.JSONDecodeError as e: