$nicks{$session->{ID}} = $session->{PLAYER}->get('nickname') 
    unless $session->{PLAYER}->anonymus;
[download]

Does it have anything to do with the fact that "anonymus" is misspelled, and should be spelled "anonymous"?

Actually, as I look at it, I doubt that's contributing to the specific problem you're reporting, but once you solve the primary problem, you might find that the misspelling also needs to be addressed before everything runs as it should. ;)