Menus: Limit mapping to registered locations

Weeds out orphaned locations, so their information will not continue to be mapped to future themes.

Fixes #42121.

Built from https://develop.svn.wordpress.org/trunk@41811


git-svn-id: http://core.svn.wordpress.org/trunk@41645 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/nav-menu.php

@@ -1085,6 +1085,7 @@ function _wp_menus_changed() {
  */
 function wp_map_nav_menu_locations( $new_nav_menu_locations, $old_nav_menu_locations ) {
 	$registered_nav_menus   = get_registered_nav_menus();
+	$new_nav_menu_locations = array_intersect_key( $new_nav_menu_locations, $registered_nav_menus );
 
 	// Short-circuit if there are no old nav menu location assignments to map.
 	if ( empty( $old_nav_menu_locations ) ) {

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9-beta1-41810';
+$wp_version = '4.9-beta1-41811';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.