Hi,
I checked the line 2157 of the file administrator/components/com_hikashop/classes/filter.php in the install package of HikaShop Business 5.0.3 available on our website and I see no count() call there:
i.imgur.com/Rs4Pbry.png
So first, download again the install package of HikaShop Business on our website and install it again on yours. Then, check if you still have the error. If you do, the line number should be different. In that case, please provide the new line number so that we can look into it.
If not, then it means that the version of the filter.php file is not the one from the install package. In that case, rename the file via FTP to something else in order to deactivate it and install the HikaShop install package again. It will add the filter.php from the package.
Then, please try again.