Media: 404 images show as empty space in the list and detail.
Original issue: https://github.com/wordpress-mobile/WordPress-Android/issues/210
To reproduce. On a self hosted blog, add some media attachments to your blog. Login to the server and manually move / delete the image files. Go to the app and view the media feature. The media items with the missing images will show a placeholder in the list but if you tap the list it will disappear. The detail always shows empty space where the image should be. A 404 image might be nice. Maybe a bit of an edgecase but I'm thinking of blogs with missing media due to bad migrations or broken gallery plugins.
2.5 beta 4(?) / Nexus 7
I checked in both the Media section and in the editor > Add Media > Select from media library, and in both places I see a placeholder that always appears (never disappears from the list) for the broken image:

Trying to add that image to a post results in a broken image in the editor:

That feels like decent behavior for broken images in both places. Are there additional improvements we'd like to make to either the Media section or the editor in this case?
Tested on Nexus 9, Android 6.0.1, alpha-4.
Based on discussion about this issue:
we could have a better "broken" image representation in the editor (full width we could tap to delete for example)
This would be nice to have, but isn't essential.