To reproduce, navigate to the following URL:
https://en.wikipedia.org/w/index.php?title=User:PleaseStand/Sandbox&oldid=610241510
Under the heading {{Special:WhatLinksHere}}, a form is shown. I would expect to see either an error message or nothing instead.
Version: 1.24rc
Severity: trivial
URL: https://en.wikipedia.org/w/index.php?title=User:PleaseStand/Sandbox&oldid=610241510