Hi,
I'm not sure why you've titled your subject "loading time" as these notice messages won't change anything in the loading speed of your pages.
Also, these notice messages are not "real" errors. They are just messages displayed for the developer as some edge case is not handled properly but has no impact on the processing of the page. So you could just ignore them.
But I thank you for reporting them. We've added a fix to the code so that these notice messages don't happen anymore for the next release of HikaShop.
We've added the patches also to the install package available on our website. So if that really bothers you, you can download the install package on our website and install it on yours and that way you won't get these notices anymore.