Twenty Thirteen doesn't pad images that are inserted into a post on the same line

[ryan]

When multiple images are inserted into a post at the same time there are often inserted all on the same line. 2013 doesn't pad these images. Screenshot attached.

Here's some example content. This is created by inserting multiple images in one go with the media modal.

<a href="http://ryan.boren.me/2013/05/01/limestone-wall/img_2964/" rel="attachment wp-att-5382"><img class="alignnone size-full wp-image-5382" alt="Limestone Wall" src="http://ryan.files.wordpress.com/2013/05/img_2964.jpg" width="640" height="480" /></a> <a href="http://ryan.boren.me/2013/05/01/limestone-wall/img_2965/" rel="attachment wp-att-5383"><img class="alignnone size-full wp-image-5383" alt="Limestone Wall" src="http://ryan.files.wordpress.com/2013/05/img_2965.jpg" width="640" height="480" /></a>

[ryan]

Accidental dupe of #24238.