Beta 6 RSS Feeder

So, I upgraded my site to Beta 6 and I really like all the new changes. However I was trying to create a RSS Feeder/Forum thingy and I keep getting an error. Not sure, how to fix it...

Error Image

For those that don't like Images...
Error Text said:

Fatal error: Call to a member function getTimestamp() on a non-object in /home/divineg1/public_html/Riot/forum/library/XenForo/Model/Feed.php on line 189
Line 1052
Also... If someone can take a look at my first post. It'd be greatly appreiacted.

Thanks in advance,