Field field_customer_email is unknown

Closes #3274524 Field field_customer_email is unknown

src/PluginForm/OffsiteRedirect/OffsitePaymentForm.php

@@ -35,7 +35,7 @@ class OffsitePaymentForm extends PaymentOffsiteForm {
     $amount = $payment->getAmount()->getNumber();
     $order_amount = $precision ? $amount : bcmul($amount, 100, 0);
     $order = $payment->getOrder();
-    $email = $order->getBillingProfile()->get('field_customer_email')->getString();
+    $email = $order->getEmail();
     $params = [
       'currency' => $currency,
       'returnUrl' => $form['#return_url'],