Describe the bug

If kirby() (or any object depending on it) is called from within config.php, Kirby runs into an endless loop as it seems to load the config file over and over.

To Reproduce

Use the following config.php:

<?php

kirby();

return [
  // empty
];

Expected behavior

The kirby() object should already be accessible from the config.

Kirby Version

Kirby 3.1.3

Additional context

Forum thread: https://forum.getkirby.com/t/out-of-memory-with-config-variable/13946?u=lukasbestle