When creating a new graph, undefined variable errors may be recorded

```
2023/01/31 16:46:28 - CMDPHP PHP ERROR WARNING Backtrace: (/graphs_new.php[51]:get_allowed_ajax_hosts(), /lib/auth.php[3182]:CactiErrorHandler())
2023/01/31 16:46:28 - ERROR PHP WARNING: Undefined variable $user_id in file: /var/www/localhost/htdocs/cacti/lib/auth.php on line: 3182
```