Hi,
This indicates that something is trying to load the data of a currency based on its currency code, but the currency entry in the hikashop_currency table in the database doesn't exist.
It could be the case if, for example, you migrated the hikashop_config table where the main currency setting value is stored, while not migrating the hikashop_currency table, and that you previously had created a custom currency via the menu System>Currencies and you were using it as you main currency.
Or more simply, if you were using a currency as main currency and then you either deleted it, or changed its currency code via the System>Currencies menu.
So basically, that's something which should not happen normally.
Add the code:
if(empty($element))
return;
after the line:
function checkLocale(&$element) {
in the file administrator/components/com_hikashop/classes/currency.php and it should prevent the error.
We'll include the change for the next version of HikaShop.