Fatal error: Uncaught Error: Call to undefined function is_404() in /var/www/html/wp-includes/class-wp.php:640 Stack trace: #0 /var/www/html/wp-includes/class-wp.php(718): WP->handle_404() #1 /var/www/html/wp-includes/functions.php(960): WP->main('') #2 /var/www/html/wp-blog-header.php(16): wp() #3 /var/www/html/index.php(22): require('/var/www/html/w...') #4 {main} thrown in /var/www/html/wp-includes/class-wp.php on line 640