JsonSchema: fix input metadata when disabled

Author: soyuka

src/JsonSchema/SchemaFactory.php

@@ -230,7 +230,7 @@ private function getMetadata(string $resourceClass, string $type = Schema::TYPE_
             $inputOrOutput = $resourceMetadata->getTypedOperationAttribute($operationType, $operationName, $attribute, ['class' => $resourceClass], true);
         }
 
-        if (null === ($inputOrOutput['class'] ?? null)) {
+        if (false === ($inputOrOutput['class'] ?? false)) {
             // input or output disabled
             return null;
         }