GraphQL: Handle properly keys for pointer fields (#6499)

* Fix Unknow type bug on overloaded types

* check args too

* Additional fix to detect custom fields on pointer

src/GraphQL/loaders/parseClassQueries.js

@@ -14,7 +14,14 @@ const getParseClassQueryConfig = function(
   return (parseClassConfig && parseClassConfig.query) || {};
 };
 
-const getQuery = async (parseClass, _source, args, context, queryInfo) => {
+const getQuery = async (
+  parseClass,
+  _source,
+  args,
+  context,
+  queryInfo,
+  parseClasses
+) => {
   let { id } = args;
   const { options } = args;
   const { readPreference, includeReadPreference } = options || {};
@@ -39,7 +46,7 @@ const getQuery = async (parseClass, _source, args, context, queryInfo) => {
     config,
     auth,
     info,
-    parseClass
+    parseClasses
   );
 };
 
@@ -80,7 +87,14 @@ const load = function(
       ),
       async resolve(_source, args, context, queryInfo) {
         try {
-          return await getQuery(parseClass, _source, args, context, queryInfo);
+          return await getQuery(
+            parseClass,
+            _source,
+            args,
+            context,
+            queryInfo,
+            parseGraphQLSchema.parseClasses
+          );
         } catch (e) {
           parseGraphQLSchema.handleError(e);
         }