isDraft function (content with database) not working anymore when upgrading to kirby4

Hi,
I’m working with the code from this tutorial from the website.

But when i update my project to kirby4 the isDraft function is not working. It’s not possible to create a new item when i override this function.
I think the $this->content() causes troubles at that point. Any one know how to fix this so that i can still use draft/unlisted/listed in my project.

public function isDraft(): bool
{
    return in_array($this->content()->status(), ['listed', 'unlisted']) === false;
}

I’m aware of the issue (Content from a database Error - #8 by texnixe), but haven’t managed to look into it yet.