picture: Flip pass condition on the media="," test and add a another test

I had misunderstood how CSS grammar works.

http://dev.w3.org/csswg/mediaqueries-4/#typedef-media-query-list
http://dev.w3.org/csswg/mediaqueries-4/#typedef-media-query
http://dev.w3.org/csswg/css-values/#comb-one
http://dev.w3.org/csswg/mediaqueries-4/#error-handling

The empty string is not a valid `<media-query>` and so `media=","` is equivalent to `media="not all,not all"`