Steps to reproduce:

1.Click on the Edit button for a page
2.Insert a image in the page
3.Go to the media settings and add another image as caption
4.Save the page
5.Reopen the editor .
6.Open the image settings and delete the image as caption.
7.Undo the action
8.Click on the media settings button for the image that is as caption

Observed result:
A media settings dialog box appears with no content but it cannot be crossed out .Also the "apply changes" button does not work therefore editor becomes unresponsive.

Version: unspecified
Severity: normal