The files preview shows up underneath the show changes dialog when a picture is clicked on

Steps

1. make an attachment picture to a page, and add it to the page
2. ensure collab edit is on, and have someone make changes to the page
3. update the page, show up the changes dialog, and see the changes
4. click on the image

What happened...
The image shows up as a files preview, but the preview is underneath the dialog.

What should have happened...
The preview should be above the dialog. Or not be able to preview in the show diffs view.