It looks like the link pointing here was faulty. Maybe try searching?
?php /** * The template for displaying 404 pages (not found). * * @link https://codex.wordpress.org/Creating_an_Error_404_Page * * @package Astra * @since 1.0.0 */ if ( ! defined( 'ABSPATH' ) ) { exit; // Exit if accessed directly. } get_header(); ?>