Customizer: Register controls and settings for nav_menu_locations even when there are no menus yet.

This change ensures that the first menu created can be assigned to a location without first saving and reloading the Customizer.

Props markoheijnen.
Fixes #32858.


git-svn-id: https://develop.svn.wordpress.org/trunk@33094 602fd350-edb4-49c9-b593-d223f7449a82

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

@@ -2545,6 +2545,7 @@
 	 * @returns {string}
 	 */
 	function displayNavMenuName( name ) {
+		name = name || '';
 		name = $( '<div>' ).text( name ).html(); // Emulate esc_html() which is used in wp-admin/nav-menus.php.
 		name = $.trim( name );
 		return name || api.Menus.data.l10n.unnamed;