Service Desk's Customers don't appear when 'All access levels' filter is selected

Summary

On the User Management, Service Desk's Customers (with restricted portal access only) don't appear when no filter is selected, which technically should display all users. They only appear when the 'Restricted portal' option is selected.

Steps to Reproduce

1. Go to the User Management
2. In the 'Users' tab clear all selected filters

Expected Results

Service Desk's Customer should appear alongside JIRA users.

Actual Results

Only JIRA users appear when no filters are applied.

Workaround

Select the 'Restricted portal' filter.