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: http://core.svn.wordpress.org/trunk@22046 1a063a9b-81f0-0310-95a4-ce76da25c4cd