Last modified: 2014-06-24 01:45:58 UTC
Author and source fields are sometimes not emptied. When this happens on prev/next, and the new image has no author/source information, the info for the wrong image gets displayed. this.$credit.empty() does get called, but on the wrong element (something that's not in the DOM). At a glance, this is related to truncatableTextField somehow.
The steps to reproduce are pretty strange - see this comment for details: https://www.mediawiki.org/w/index.php?title=Talk%3AMultimedia%2FAbout_Media_Viewer&diff=1045248&oldid=1045222