Error happens when Chracteristics are added to a product

-- HikaShop version -- : 4.7.1
-- Joomla version -- : 4.2.8
-- PHP version -- : 8.1
-- Browser(s) name and version -- : Chrome 109.0.5414.119
-- Error-message(debug-mod must be tuned on) -- : Attempt to modify property "characteristics" on null
JROOT/components/com_hikashop/views/product/tmpl/show_block_characteristic.php:23

If any characteristic is added, either the ones that were created with the demo content, or a new one created afterwards, the same error appears on that specific product.
If the product has no chracteristics added, no error is present.

Hi,

I suppose you added the characteristic to the product but didn't add any variant to the product yet. So the product is in an "in-between" state leading to that error.

Change the line:
if(empty($this->element->characteristics))
to:
if(empty($this->element->characteristics) || empty($this->element->main->characteristics))
in the file /components/com_hikashop/views/product/tmpl/show_block_characteristic.php and it should avoid the error.
But you'll still have to add variants to your product.