Shipping Estimator Sidebox gives PHP warnings and just act strange...

Hi all, I know that this mod hasn't been updated for a while, but I tried to install it anyways, I did however ran into a few problems.

1. When a user is not signed in it just tells me :
   Warning: Creating default object from empty value in /sites/www.mydomain.org/public_shop/includes/modules/sideboxes/shipping_estimator.php on line 98.

2. Once I activate the sidebox I cannot add any more products to my cart. The page reloads after I click "Buy now" but no product made it to the cart :/.

• some other weird / unexpected behavior when I click anywhere on the sidebox.

It's sad because I think this sidebox would fit just perfect on my store. Are there any plans to make this mod fully compatible with ZC 1.5x (and the later PHP versions, I guess...) ?

Please let me know what the status is here. Thanks!

Best regards

Peter