When going through a non-index entry page, e.g. api.php, without the wiki set up, the message that is shown has corrupted urls (e.g. for me, http://localhost/mw/api.phpconfig/index.php), on both the link and the image.
It's a reasonably rare occurence, but may happen on public wikis with bots when updating the software, or accidentally moving/deleting your config.
Patch tested to merge fine on r40691 of trunk
attachment wikinotsetup_invalidpath.patch ignored as obsolete