Send redirect subtype for Riverty installments

ISSUE: CR-SET-45

Author: dokmanovicsofija

src/Handlers/RivertyPaymentTrait.php

@@ -74,7 +74,11 @@ protected function getAdyenPaymentRequest(
         // flow, and the only one without an Adyen Web component to set the subtype itself - the
         // plain redirect component it falls back to sends none.
         if (static::class === RivertyInstallmentsPaymentMethodHandler::class) {
-            $paymentRequest->getPaymentMethod()?->setSubtype('redirect');
+            $rivertyPaymentMethod = $paymentRequest->getPaymentMethod();
+
+            if (!is_null($rivertyPaymentMethod)) {
+                $rivertyPaymentMethod->setSubtype('redirect');
+            }
         }
 
         if (!$this->rivertyFingerprintParamsProvider->isProfileTrackingEnabled(