[Address] Handle adress exists validation in case when address does not belong to any customer

[hurricane-voronin]

Hi there,
I've got an error during validation of address existence in case when it does not belong to any customer:
see AddressExistsValidator

if ($address->getCustomer()->getEmail() !== $user->getEmail()) {
    return $this->context->addViolation($constraint->message);
}

[mamazu]

Hey,
thanks for your contribution. This looks like an issue that should be fixed. Would you mind, to add tests for you new behaviour?

[diimpp]

Fixes #705

[mamazu]

I have pushed tests to this branch and it is ready to be merged.

[lchrusciel]

Thanks, Denys! 🥇