bug in "thanks" feature?

[Grimm]

I thanked a post by clicking the scroll wheel on my mouse (this opens a link in a new tab, so you can thank without changing the tab you're on). The thank was registered properly but the new tab that opened showed this:

Fatal error: Class 'messenger' not found in /var/www/crawl.develz.org/htdocs/tavern/includes/functions_thanks.php on line 511

[TehDruid]

I get this almost every time I thank MyO. The thanks does register, though.