Notice Undefined index: email_match in uc_checkout_pane_customer()

When setting "Require e-mail confirmation in checkout for anonymous customers." in
Store » Konfiguration » Checkout settings
and afterwards going through the order-process, I get these notices:

Notice: Undefined index: email_match in uc_checkout_pane_customer() (line 76 in ...sites/all/modules/ubercart/uc_cart/uc_cart_checkout_pane.inc).
Notice: Undefined index: email_match in uc_checkout_pane_customer() (line 77 in ...sites/all/modules/ubercart/uc_cart/uc_cart_checkout_pane.inc).

on the checkout-page.