Multisafepay Exception after Checkout

-- HikaShop version -- : 5.0.0
-- Joomla version -- : 4.3.4
-- PHP version -- : 8.1.2
-- Browser(s) name and version -- : Firefox 117.0.1
-- Error-message(debug-mod must be tuned on) -- : 0
MultiSafepay\ValueObject\Customer\Address::addState(): Argument #1 ($state) must be of type string, null given, called in /var/www/breisig.live/www/htdocs/plugins/hikashoppayment/multisafepay/multisafepay.php on line 63

Hello,
after checkout and going to Multisafepay we get the following error:

0
MultiSafepay\ValueObject\Customer\Address::addState(): Argument #1 ($state) must be of type string, null given, called in /var/www/breisig.live/www/htdocs/plugins/hikashoppayment/multisafepay/multisafepay.php on line 63

We need help to fix this issue, thanks.
Michael

[Moderator :] Please don't edit your message long after posting it.
This disrupts our ticketing system and increases our response times for everyone, including you.
If you have new items post another message.
Thank you for your attention