Admin:User Browser in admin tab is not working with JAC data

Steps:
1. Login to JIRA.
2. Click on "Admin" tab.
3. Click on "User Browser" to access the user list.

Result:
1. Nothing happens and user sees a JAVA heap error in logs. Log file attached.
2. Heap memory is set to 768mb

Expected:
1. No issues and user should be able to access user browser without any error.