#32596: Category Update API resets available_sort_by to use config value - GraphQL test fix.

Author: engcom-Foxtrot

dev/tests/api-functional/testsuite/Magento/GraphQl/Catalog/CategoryTest.php

@@ -111,7 +111,7 @@ public function testCategoriesTree()
             $responseDataObject->getData('category/url_key')
         );
         self::assertEquals(
-            [],
+            null,
             $responseDataObject->getData('category/children/0/available_sort_by')
         );
         self::assertEquals(
@@ -185,7 +185,7 @@ public function testRootCategoryTree()
             $responseDataObject->getData('category/url_key')
         );
         self::assertEquals(
-            [],
+            null,
             $responseDataObject->getData('category/children/0/available_sort_by')
         );
         self::assertEquals(