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.

Built from https://develop.svn.wordpress.org/trunk@44640


git-svn-id: http://core.svn.wordpress.org/trunk@44471 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/js/media-views.js

@@ -6549,6 +6549,9 @@ Attachment = View.extend(/** @lends wp.media.view.Attachment.prototype */{
 		} else {
 			selection.add( this.model );
 		}
+
+		// Trigger an action button update.
+		this.controller.trigger( 'selection:toggle' );
 	}
 });
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-beta1-44639';
+$wp_version = '5.1-beta1-44640';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.