Why is withUser null?

[Pavel Grinevich]

public function getThreads()
    {
        $conversations = Talk::threads();

        if (!$conversations) {
            return response()->json(["message" => trans('messages.threads.not_found')], 404);
        }

        return response()->json($conversations, 200);

[Pavel Grinevich]

This is my mistake) I sent messages to non-existing users.