Properly render the image details modal when the image references an invalid attachment.

props gcorne.
fixes #27537.


git-svn-id: https://develop.svn.wordpress.org/trunk@27756 602fd350-edb4-49c9-b593-d223f7449a82
Customizer: Improve accessibility.

Prevent the form only from saving when enter is pressed on a select element or an input, which hasn't the button type.

props westonruter, ocean90.
fixes #26633.

git-svn-id: https://develop.svn.wordpress.org/trunk@27757 602fd350-edb4-49c9-b593-d223f7449a82