could not duplicate or edit product by saleman account

[vietdiesel]

hi . i have this issue with 1.7.6 . i updated to 1.7.8 still same issue . contacted with hosting provider they told me issue from soucre code 

Type error: Argument 1 passed to PrestaShopBundle\Model\Product\AdminModelAdapter::__construct() must be an instance of PrestaShop\PrestaShop\Adapter\LegacyContext, instance of Product given, called in /home1/xxxx/public_html/src/PrestaShopBundle/Controller/Admin/ProductController.php on line 1260

[Symfony\Component\Debug\Exception\FatalThrowableError 0]

please help