Customer List warning | WordPress.org

Getting the warning above the Customers title on the page [MY_SITE]/wp-admin/admin.php?page=salon-customers. It’s a local testing site, running on Server: XAMPP (PHP 8.2.12); OS: Windows 11 home; Browsers: Chrome and Edge [both up to date]) .

Warning: Undefined array key "" in [MY_SITE]\wp-content\plugins\salon-booking-system\src\SLN\Admin\Customers\List.php on line 110

I don’t have any other plugins or themes (twenty-something). I deleted all bookings, assistants, customers, services. Made no difference.

Not sure if this will affect functionality, but doesn’t fill me with confidence as am looking to purchase the commercial version.