Apply suggeston from Paolo

Co-authored-by: Paolo <[email protected]>

Author: westonruter

src/wp-admin/menu-header.php

@@ -264,7 +264,7 @@ function _wp_menu_output( $menu, $submenu, $submenu_as_parent = true ) {
 						&& ! file_exists( ABSPATH . "/wp-admin/$sub_file" ) )
 				) {
 					// If admin.php is the current page or if the parent exists as a file in the plugins or admin directory.
-					if ( ( ! $admin_is_parent && file_exists( WP_PLUGIN_DIR . "/$menu_file" ) && ! is_dir( WP_PLUGIN_DIR . "/{$item[2]}" ) ) || file_exists( $menu_file ) ) {
+					if ( ( ! $admin_is_parent && file_exists( WP_PLUGIN_DIR . "/$menu_file" ) && ! is_dir( WP_PLUGIN_DIR . "/{$item[2]}" ) ) || file_exists( ABSPATH . 'wp-admin/' . $menu_file ) ) {
 						$sub_item_url = add_query_arg( array( 'page' => $sub_item[2] ), $item[2] );
 					} else {
 						$sub_item_url = add_query_arg( array( 'page' => $sub_item[2] ), 'admin.php' );