Hi,
You can see to modify the line in order to add some checks to verity that the constant exists.
Otherwise, you can do what Nicolas first recommended : to deactivate the display of these warning, in your Joomla global configuration (or in your php.ini).
If you set the "error reporting level" to "none" ; you won't display anymore the PHP error messages, like it should be on all production websites.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.