Add PaymentHandler reference when validating the merchant

https://bugs.webkit.org/show_bug.cgi?id=241520
<rdar://problem/94609087>

Reviewed by Wenson Hsieh.

* Source/WebCore/Modules/paymentrequest/PaymentRequest.cpp:
(WebCore::PaymentRequest::completeMerchantValidation):

Canonical link: https://commits.webkit.org/251469@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@295463 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebCore/Modules/paymentrequest/PaymentRequest.cpp

@@ -604,7 +604,8 @@ ExceptionOr<void> PaymentRequest::completeMerchantValidation(Event& event, Ref<D
             return;
         }
 
-        auto exception = activePaymentHandler()->merchantValidationCompleted(m_merchantSessionPromise->result());
+        Ref activePaymentHandler = *this->activePaymentHandler();
+        auto exception = activePaymentHandler->merchantValidationCompleted(m_merchantSessionPromise->result());
         if (exception.hasException()) {
             abortWithException(exception.releaseException());
             return;