Hi,
The message
PHP Warning: Creating default object from empty value in /home/ark/public_html/components/com_hikashop/views/category/view.feed.php on line 119
is a normal information message for developers because an object attribute is set without first initializing the object. Before a certain version of PHP, this didn't matter but PHP started displaying these messages to help developers when debugging.
This however won't help an attacker.
And it's about the same for
PHP Notice: Undefined property: checkoutController::$controllers in /home/ark/public_html/components/com_hikashop/controllers/checkout.php on line 1838
So your problem comes from something else.
To find where it could be, you need to look at the access log of your web server for URLs with strange parameters around the time the website was hacked.
I would recommend the help of a professional like
www.aesecure.com/en/
in order to secure your website because if it's been hacked once, it will be hacked again if you don't take steps to prevent that.