Object reference error

Getting error:Object reference not set to an instance of an object in Assign activity
passing datatable from one workflow to another workflow
Uipath execution started
Invoke workflow file: Assign : Object reference not set to an instance of an object.
Uipath execution ended in:

Hi ,
As you mentioned your trying to pass datatable from one workflow to another workflow . Hope you have created datatable as the argument in child workflow and importing to the variable in parent workflow.