When an answer has been deleted because the OP deleted his question, the "undelete" link is still shown for that answer.
(I reused a screenshot I took for another issue report; that is why the "undelete" link is not highlighted.)
Clicking on it doesn't have any effect, as you just get a dialog box.
In such cases, the link should not be shown, if I am not able to undelete my post. Maybe a moderator is able to undelete a post in this case (I don't see why, though), but I am not a moderator.