When you follow a link to a diff for a page that has been deleted, you get an "The database did not find the text of a page that it should have found" error. But you also get a pointless "Mark this page as patrolled" link, which just returns an error.
Version: unspecified
Severity: trivial
URL: https://www.mediawiki.org/w/index.php?oldid=534499&rcid=605092