Fixed missing ArrayHelper class on export. Updated the table class to also use StringHelper instead of JString.

admin/controllers/custom_codes.php

@@ -12,6 +12,8 @@
 // No direct access to this file
 defined('_JEXEC') or die('Restricted access');
 
+use Joomla\Utilities\ArrayHelper;
+
 /**
  * Custom_codes Controller
  */