Fixed #34620 -- Fixed serialization crash on m2m fields without natural keys when base querysets use select_related().

Regression in 19e0587ee5.

Thanks Martin Svoboda for the report.

tests/serializers/test_json.py

@@ -38,7 +38,8 @@ class JsonSerializerTestCase(SerializersTestBase, TestCase):
       %(first_category_pk)s,
       %(second_category_pk)s
     ],
-    "meta_data": []
+    "meta_data": [],
+    "topics": []
   }
 }
 ]