add nullable format

Author: eltharin

components/serializer.rst

@@ -1486,11 +1486,11 @@ having unique identifiers::
 
     $encoder = new JsonEncoder();
     $defaultContext = [
-        AbstractNormalizer::CIRCULAR_REFERENCE_HANDLER => function (object $object, string $format, array $context): string {
+        AbstractNormalizer::CIRCULAR_REFERENCE_HANDLER => function (object $object, ?string $format, array $context): string {
             return $object->getName();
         },
     ];
-    $normalizer = new ObjectNormalizer(null, null, null, null, null, null, $defaultContext);
+    $normalizer = new ObjectNormalizer(defaultContext: $defaultContext);
 
     $serializer = new Serializer([$normalizer], [$encoder]);
     var_dump($serializer->serialize($org, 'json'));