Fatal error (after update to 2.6.4?)

-- HikaShop version -- : 2.6.4.
-- Joomla version -- : 3.6.2
-- PHP version -- : 5.6.18
-- Browser(s) name and version -- : chrome 53.0.2785.89
-- Error-message(debug-mod must be tuned on) -- : Fatal error: Call to undefined function first() in .../components/com_hikashop/views/product/view.html.php on line 1597

Hi!
Yesterday I updated to 2.6.4. Today, when I make a new product en I test it on the front-end. In productlist I click on the order button or the titel to read more about the product. I don't get the more info page but I get a Fatal error.

Fatal error: Call to undefined function first() in .../components/com_hikashop/views/product/view.html.php on line 1597

Products that already existed don't have this error. When I duplicate an existing product, I get the same error too.

Please help? Whats wrong?

Thank you! That solved it.