Hi,
It seems that HikaShop wasn't install properly.
It thinks that it is not on Joomla 3, at least for some of the features. For example, the menu of HikaShop is displaying itself as if it was on a Joomla 2.5 and not 3.0. And that error you have comes from the same origin I think.
Try to install the HikaShop install package of the 2.6.3 again on your website. That should hopefully help. Also, just before doing that, rename the folder administrator/components/com_hikashop/ via FTP in order to avoid access right issues during the installation so that it can force the use of the latest version files.