Use get_registered_nav_menus() in has_nav_menu().

props voldemortensen.
fixes #29461.
Built from https://develop.svn.wordpress.org/trunk@29717


git-svn-id: http://core.svn.wordpress.org/trunk@29491 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/nav-menu.php

@@ -142,9 +142,8 @@ function get_nav_menu_locations() {
  * @return bool Whether location has a menu.
  */
 function has_nav_menu( $location ) {
-	global $_wp_registered_nav_menus;
-
-	if ( ! isset( $_wp_registered_nav_menus[ $location ] ) ) {
+	$registered_nav_menus = get_registered_nav_menus();
+	if ( ! isset( $registered_nav_menus[ $location ] ) ) {
 		return false;
 	}