TinyMCE gallery preview: fix errors when an image doesn't have/is smaller than  thumbnail size, props gcorne, see #26959
Built from https://develop.svn.wordpress.org/trunk@27580


git-svn-id: http://core.svn.wordpress.org/trunk@27423 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE gallery preview: fix editing the same gallery multiple times. Instead of .data() use .attr('data-...'), jQuery caches the former. Props gcorne, see #26959
Built from https://develop.svn.wordpress.org/trunk@27581


git-svn-id: http://core.svn.wordpress.org/trunk@27424 1a063a9b-81f0-0310-95a4-ce76da25c4cd