fix empty username for Anonymous user

I misinterpreted this bug, actually the empty text belongs to Anonymous user
($row->name doesn't returns any name)
this will be fixed altogether handling this filter by u.uid instead of u.name, since it is no longer an autocompletion but a
which might have duplicated names/realnames

Note: if this gets committed first then a re-roll would be required for #642164: filter by u.uid instead of u.name and vice versa.

bug fix: use double equals (instead of three) to compare $row->uid == 0