Guest checkout , register button not working

Hi,

I am using the latest Hikashop Business, on J 3.0.3.
I have configured my shop for Guest checkout only: (login: no, Registration: no) but when I test it with an email address I already used with an order, the "Register" button does not work.

If I correct the e-mail address in the form, using a email address I have not used before, the "register" button does work, and I can continue.

(When I enabled Joomla debugger, it does not return any errors, only two notices:

Notice: Trying to get property of non-object in /home/domain/public_html/testspace/administrator/components/com_hikashop/classes/user.php on line 544
Notice: Trying to get property of non-object in /home/domain/public_html/testspace/administrator/components/com_hikashop/classes/user.php on line 548
)

I hope you can help.

best regards,

Tom