Problem in grouping the resources

In resource panel , there is no tasks assigned so that folder is not showing but when we drag any tasks , un-assign folder is showing up:
Sample video is provided:

Hello,
Right now, Gantt has different behavior for the group feature. If the relation_property has the String or Number, the empty group is not added. If it is an array, you can see the “empty” group:
https://snippet.dhtmlx.com/5/d97ac7440

Usually, the default group (“None” is the default name) is displayed when there are tasks that don’t fit any group. But if we have project tasks that are not displayed, Gantt still adds that group:
https://snippet.dhtmlx.com/yytxfdb0

It will be fixed in the future, but I cannot give you any ETA.

If you don’t want to see the None group, you can hide that task with the onBeforeTaskDisplay event handler:
https://docs.dhtmlx.com/gantt/api__gantt_onbeforetaskdisplay_event.html

Here is the snippet:
https://snippet.dhtmlx.com/mfucm6yo