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

admin/compiler/joomla_3/JModelItem_custom_admin.php

@@ -17,6 +17,8 @@ defined('_JEXEC') or die('Restricted access');
 // No direct access to this file
 defined('_JEXEC') or die('Restricted access');
 
+use Joomla\Utilities\ArrayHelper;
+
 /**
  * ###Component### ###SView### Model
  */