Error viewing new orders - upgraded from prestashop 1.7.6.9 to 1.7.8.2

[Cheetah1]

I recently upgraded to 1.7.8.2 from 1.7.6.9, and everything seemed to be working ok, but I noticed today when trying to view a new order it is crashing with this message:

Oops... looks like an unexpected error occurred.
Call to a member function isLogged() on null
[Symfony\Component\Debug\Exception\FatalThrowableError 0]

When I turn on "debug" mode and press the order again it displays this:

ContextErrorException
HTTP 500 Internal Server Error
Warning: Declaration of Cart::getPackageShippingCost($id_carrier = NULL, $use_tax = true, ?Country $default_country = NULL, $product_list = NULL, $id_zone = NULL) should be compatible with CartCore::getPackageShippingCost($id_carrier = NULL, $use_tax = true, ?Country $default_country = NULL, $product_list = NULL, $id_zone = NULL, bool $keepOrderPrices = false)
 
 
ContextErrorException
in override/classes/Cart.php (line 605)
    /*    * module: kbfreedelivery    * date: 2022-02-21 02:22:09    * version: 1.0.3    */    public function getPackageShippingCost($id_carrier = null, $use_tax = true, Country $default_country = null, $product_list = null, $id_zone = null)    {        if ($this->isVirtualCart()) {            return 0;        }        if (!$default_country) {

 

Anyone have any idea how to fix this?

Would definitely appreciate any advice!

Thanks