Duplicate User pop-up info panel has null last seen date

[Stuart Wright]

last seen: Jan 1, 1970.
Doesn't apply to everyone, but did apply to a couple of people I clicked on

 

[Andrej]

Duplicate of http://xenforo.com/community/threads/invisible-users-have-malfunctioning-last-seen-date.51557/

 

[Stuart Wright]

Yep, just spotted it, apologies.