When i add this little snippet to use custom block icons to my block_editor in twill.php

"directories" => [
            "source" => [
                "icons" => [
                    base_path("vendor/area17/twill/frontend/icons"),
                    resource_path("views/twill/icons"),
                ],
            ],
        ],

It gives me this error (see screenshot), i'm using twill version 3.0.0-rc4. Is this a bug or am i doing something wrong?