looking for clarification on error message with Opencart Backend

I installed a helpdesk plugin  in my opencart 3 based website and now When I go to Login to the admin Panel, after logging in I am presented with this error:

Warning: Attempt to read property "TsDefault" on null in /home/storage/modification/admin/controller/common/column_left.php on line 21

My issue is in that file I do not see any reference to TsDefault? Nor do I know how to fix it inside my Custom Lithium Ion Battery Pack Manufacturer kindly guide me, any kind of help would be appreciated. Thanks in Advace.