When splitting a shared 'nav_menu' term, ensure that nav items and theme locations are retained.

Props boonebgorges, dd32.
Fixes #33187.

git-svn-id: https://develop.svn.wordpress.org/trunk@33611 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/nav-menu.php

@@ -315,6 +315,8 @@ function wp_update_nav_menu_object( $menu_id = 0, $menu_data = array() ) {
 	if ( is_wp_error( $update_response ) )
 		return $update_response;
 
+	$menu_id = (int) $update_response['term_id'];
+
 	/**
 	 * Fires after a navigation menu has been successfully updated.
 	 *