error rss

I do not know if it's done on purpose or not, however if you click on the icon rss feed from this error:

Fatal error: Class wbb \ data \ thread \ FeedThread contains 1 abstract method and must Therefore be declared abstract or implement the remaining methods (wcf \ data \ IMessage :: IsVisible) in / var / www / WoltLab / beta / lib / data / thread / FeedThread.class.php on line 92

Ok, thanks