(In reply to comment #0)

Fatal error: Call to a member function getPreviousRevisionID() on a non-object

Line 560 & 573

560 : $prev = $this->getTitle()->getPreviousRevisionID(
$this->getId() );

573 : $next = $this->getTitle()->getNextRevisionID(
$this->getId() );

I think that getTitle doesn't give a Revision object, and calling on it
getPreviousRevisionID and getNextRevisionID maybe is wrong.

Actually, getPreviousRevisionID() and getNextRevisionID() are Title members. The problem is that $this->getTitle() doesn't return an object ("on a non-object"), so stuff goes wrong when calling getPrevious() or getNext() on Revision objects that don't have valid associated Title objects.

Fixed in r35180