-- fixed issue with im_gp_check_duplicate_task_names
   $task_hash($parent_wbs) where $parent_wbs = "Top" would throw error
   It's assumed that this err happens only when task with duplicate name appear under top parent node
   Usage is limited to provide err msg to client only, does not have an impact on further execution
   Therfore the rather pragmatic approach of setting parent_name to "" in case of empty array