Customizer: in menus, reset results when closing the 'add items' panel.

Trigger a keyup event when clearing the search field in response to closing the add item panel. The keyup event triggers a search and resets the results. Previously, the search field was cleared while the potentially blank search results were left in place making it impossible to select new menu items.

Props Blair jersyer, aranwer104, afercia.
Fixes #43333.


Built from https://develop.svn.wordpress.org/trunk@42744


git-svn-id: http://core.svn.wordpress.org/trunk@42574 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/js/customize-nav-menus.js

@@ -727,7 +727,7 @@
 			$( 'body' ).removeClass( 'adding-menu-items' );
 			$( '#available-menu-items .menu-item-handle.item-added' ).removeClass( 'item-added' );
 
-			this.$search.val( '' );
+			this.$search.val( '' ).trigger( 'keyup' );
 		},
 
 		// Add a few keyboard enhancements to the panel.