Cannot catch error when extended class is missing

Question

I try to cycle through all loaded classes, that extend a certain class. But is_subclass_of is throwing an "Class not found" Error, if the reason is an extend class that wasnt autoloaded - and i cannot catch it.

        $allClasses = 'vendor/composer/autoload_classmap.php';
            $classes=[];
            foreach ($allClasses as $name => $file){
                try {

                    if (is_subclass_of($name,'mynamespace\\project\\src\\models\\BaseWintypeModel'))
                    {
                        $classes[] = $name;
                    }

                }
                catch(\Throwable $e)
                {
                    echo "caught exception";
                }
            }

Error is e.g.

PHP Fatal Error – yii\base\ErrorException
Class 'Illuminate\Support\ServiceProvider' not found
1. in /www/fresh/vendor/nesbot/carbon/src/Carbon/Laravel/ServiceProvider.php

because

class ServiceProvider extends \Illuminate\Support\ServiceProvider