RSForm Conflict

-- HikaShop version -- : 2.2.1
-- Joomla version -- : 2.5.14
-- PHP version -- : 5.3.19
-- Error-message(debug-mod must be tuned on) -- : Fatal error: Call to undefined function hikashop_decode() in /administrator/components/com_rsform/helpers/rsform.php(479) : eval()'d code on line 3

I recently updated from Hika Business 1.5.9 to 2.2.1. Prior to updating I was using hikashop_decode to return the affiliate id in a popup form. It was working in 1.5.9 but since the update I started getting the above error. It still works fine in a normal module on the site but in a popup it seems that the decode function isn't being loaded before the popup is triggered even though the plugin order has popup plugin at the end (right before cache which is disable and before SEF)

Which file is that?

I found it.

require_once ("administrator/components/com_hikashop/helpers/helper.php");