Error: 0 JPath::clean: $path is not a string.

-- url of the page with the problem -- : www.atmospheremilazzo.com/administrator/...hikashop&ctrl=config
-- HikaShop version -- : 2.3.5
-- Joomla version -- : 3.2.1
-- Error-message(debug-mod must be tuned on) -- : 0 JPath::clean: $path is not a string.

Hello,
i have updated Hikashop from Starter to Essential version.
Now i have the error "0 JPath::clean: $path is not a string." when i try access to configuration page:
index.php?option=com_hikashop&ctrl=config

Hi,

Please check via phpMyAdmin that you have filled correct values for the keys "uploadfolder" and "uploadsecurefolder" in the table "#__hikashop_config".
If the values are correct, first do a backup, update your Joomla version, if it is still not working, please give us backend and ftp access via private message or via our contact form. Don't forget to give us the url of that topic in the message.