fix potential issue with setting geoNear.query to undefined (#6696)

* add test cases for geoNear aggregation

Test cases do not have the `query` parameter set in $geoNear aggregation stage. this is to test for a reported potential issue when the parameter is not set.

* fixed potential issue when setting the geoNear.query parameter to undefined

see dicussion in https://github.com/parse-community/parse-server/pull/6540

* fixed duplicate index name in test

src/Adapters/Storage/Mongo/MongoStorageAdapter.js

@@ -860,7 +860,7 @@ export class MongoStorageAdapter implements StorageAdapter {
           stage.$project
         );
       }
-      if (stage.$geoNear) {
+      if (stage.$geoNear && stage.$geoNear.query) {
         stage.$geoNear.query = this._parseAggregateArgs(
           schema,
           stage.$geoNear.query