Unlink most recent name of guests, not userid
Currently a user can send a link and log out quickly, resulting in the |unlink| never unlinking their message (instead it unlinks the guest### messages, which don't exist). This unlinks the current name of a user, or their most recent one if they aren't named
Merge pull request #885 from TalkTakesTime/patch-2

Unlink most recent name of guests, not userid