Hello,
Thank you for the report.
That message is just a notice and should not be displayed in a production website ; as you see it gave private information to users.
You can edit the corresponding file (checkout/login.php) and replace the line 422 :
if($params['registration_guest']) {
By
if(!empty($params['registration_guest'])) {
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.