Assigned to field is blank for the user on service request edit page for HR HELP DESK

Summary: The user is contingent worker with limited access.

Content (required): Not sure which exact privilege gives access to list of value for person search field on "assigned to"

Version (include the version you are using, if applicable): 22B

Code Snippet (add any code snippets that support your topic, if applicable): We are using custom role and HR Help desk custom agent role is already assigned to the user.

For workers with custom employee role its working fine.