Media: Improve unselecting media in the media bulk selection mode.

Disables the "Delete Selected" button when unselecting media by clicking the
"checkmark" box in the media bulk selection mode.

Props subrataemfluence, adamsilverstein.
Fixes #42239.


git-svn-id: https://develop.svn.wordpress.org/trunk@44640 602fd350-edb4-49c9-b593-d223f7449a82

src/js/media/views/attachment.js

@@ -509,6 +509,9 @@ Attachment = View.extend(/** @lends wp.media.view.Attachment.prototype */{
 		} else {
 			selection.add( this.model );
 		}
+
+		// Trigger an action button update.
+		this.controller.trigger( 'selection:toggle' );
 	}
 });