Fatal error when renewing subscription

I’m not sure how the customer got into this state, but we had a situation today where WC_QuickPay_Subscription::cart_contains_failed_renewal_order_payment() returned true on line 351 in classes/woocommerce-quickpay-order.php (inside the method get_order_number_for_api), but WC_QuickPay_Subscription::get_subscriptions_for_renewal_order() returned false, because the array of subscriptions was empty. This caused a fatal error on line 354.

I’ve solved this locally by turning the line
$order_number .= sprintf( '-%d', $subscription->get_failed_payment_count() );
into

if ( $subscription ) {
	$order_number .= sprintf( '-%d', $subscription->get_failed_payment_count() );
}
else {
	$order_number .= sprintf( '-%d', time() );
}

I’m hoping you’ll be able to add this or something similar to a future release.