minor fix

Author: mathielen

src/CXml/Processor/Processor.php

@@ -103,7 +103,7 @@ private function processMessage(Message $message, Context $context): void
      */
     private function processResponse(Response $response, Context $context): void
     {
-        $payload = $response->payload;
+        $payload = $response->payload ?? null;
 
         if (!$payload instanceof ResponsePayloadInterface) {
             return;