[ticket/11602] Do not call localize_errors() if avatars are disabled

The avatar manager's method localize_errors() shouldn't be called if
avatars are disabled in the config.

PHPBB3-11602
Merge remote-tracking branch 'marc1706/ticket/11602' into develop

* marc1706/ticket/11602:
  [ticket/11602] Do not call localize_errors() if avatars are disabled