This is not related to the plugin, the illuminate/support
helpers.php file is loaded before the kirby
setup.php file.
vendor/composer/autoload_static.php
public static $files = array (
'...' => __DIR__ . '/..' . '/symfony/polyfill-mbstring/bootstrap.php',
'...' => __DIR__ . '/..' . '/illuminate/support/helpers.php',
'...' => __DIR__ . '/..' . '/mustangostang/spyc/Spyc.php',
'...' => __DIR__ . '/../..' . '/site/plugins/kirby-blade/helpers.php',
'...' => __DIR__ . '/../..' . '/kirby/config/setup.php',
);