fix: 🐛 handle empty member_ids in group responses

ui/core/mirage/serializers/group.js

@@ -12,7 +12,7 @@ export default ApplicationSerializer.extend({
 
   _hashForModel(model) {
     const json = ApplicationSerializer.prototype._hashForModel.apply(this, arguments);
-    json.member_ids = model.memberIds;
+    if (model.memberIds.length) json.member_ids = model.memberIds;
     return json;
   }