Wikimedia Bugzilla is closed!

On a wiki without a MediaWiki:Common.css, action=raw (as called by the skin)
returns the strange content "<Common.css>" instead of an empty file,
resulting in an error on Firefox's JavaScript Console ("Error: Unexpected end of
file while searching for closing } of invalid rule set.").

*A nonexistent MediaWiki page should either return an empty file or a 404 error
(or both) when requested with action=raw
*Either the skin should not request MediaWiki:Common.css when it doesn't exist,
or an empty one should be created (MediaWiki default) (doing either would have
avoided this bug)