Settings->SearchUsers show some users more than once

When searching in "settings->searhc users" for users the result contains some users more then once.

Looks like this happens for users who are members of more than one group.

Could be repproduced by

1. create a new group
2. add a user to this new group (user should be no member of 2 groups)
3. Search for users. in "settings->search users" the changed user now is shown twice in the result

Seams that a DISTINCT is missing in the database query.