The Special:ClaimMentee page will suggest temporary account usernames in the dropdown form for the "Mentee's username" user multi-select. It should not suggest temporary accounts as they cannot be claimed as a mentee.

Steps to replicate the issue

1. Enable temporary accounts on your wiki
2. Create a temporary account by making an edit while logged out
3. Log into an account which has rights to be a mentor
4. Open Special:ClaimMentee
5. Type ~ into the username field

What happens:
The username dropdown field suggests a temporary account username

What should have happened instead:
No temporary accounts should be suggested in the dropdown field