Symfony: Form issue using Return type hinting in Doctrine Entity methods

I was being exceptionally diligent today and decided to return-type hint all of my symfony entity methods. So:

<?php

Class User {
    private string $username;
    public method getUsername(): string {}
}

all good and well, until I made a form to create a new user:

$user = new User();
$this->createForm(SignupType::class, $user);

when the form is displayed, Symfony automatically gets the properties of this new instance of User $user. But since it is a new instantiation, its username property is of course still null, which is an incorrect return type as it needs to be string.

Should I either:

1. have no return-type hinting in Symfony entities (meh);
2. set $username = '' (but hat kind of defeats the purpose of not allowing blanks and I can see all sorts of errors evolving); or
3. unmap the field on the symfony form
4. other possible solutions...