To do so, the Attachment view code had to be shifted above the Workspace view code to ensure the subview is defined (preventing errors).
Also corrects an error in `wp.media.view.Attachments.add` where it was still using the default Attachment view.
see #21390, #21809.
git-svn-id: https://develop.svn.wordpress.org/trunk@22046 602fd350-edb4-49c9-b593-d223f7449a82