Home page does not show 404

[simpleauthority]

The home page does not show a 404 message because $_GET['url'] is unset at the time of checking. The page is blank, and an error is logged:

2018/04/04 21:51:30 [error] 2990#2990: *21 FastCGI sent in stderr: "PHP message: PHP Notice:  Undefined index: url in /usr/share/nginx/html/v.craftblock.me/shorty.php on line 315
PHP message: PHP Notice:  Undefined index: format in /usr/share/nginx/html/v.craftblock.me/shorty.php on line 316" while reading response header from upstream, client: 172.69.142.45, server: v.craftblock.me, request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/var/run/php/php7.2-fpm.sock:", host: "v.craftblock.me"