Shipping price per product don't work in product with variants

-- url of the page with the problem -- : www.laputea.com
-- HikaShop version -- : 3.0.1
-- Joomla version -- : 3.5

Hello,

I set the "shipping price per product" on each product in the shop, but when I add a new product, the "shipping price" appears only in the main product, not that in the variants view.
The products are placed in a warehouse that is called "magazzino standard" I configured the shipping method by selecting the "magazzino standard", attaching screenshots.

Notice: Trying to get property of non-object in /var/www/html/administrator/components/com_hikashop/classes/product.php on line 737

I understand, but why in all other products shipping price also appear on variants?
I attach screenshots.

hello, I understand where is the problem. The shipping cost per product does not appear in variants because the products were placed in a warehouse. If I delete the warehouse, the price for the product appears in the variants.

I had two warehouses: warehouse books, standard warehouse.

I deleted both warehouses. So in "shipping methods" do not appear warehouses.
I attach screenshots.

Sorry if I insist, but I can not understand why some products are set two shipping systems!

Before I had two warehouses with two shipping costs.

Now I set the price per product and I moved all the products in one warehouse.

I set the delivery system without warehouse restrictions.

Yet when the user purchases products that were previously in two warehouses, leaving two shipping methods.

If I try to set the restriction "warehouse" in "Shipping methods", the method does not appear in the front-end, so I have to set the restriction of "no warehouse".

Am I doing something wrong?

Help me because they do not know how to bring up a single shipping method, because now there is confusion for users!

I realized that the problem does not depend on the warehouse, but the variants. We always come back to the initial problem.

If I add to cart products with variants, the system calculates a shipping method.

If I add products to cart without variation, the system calculates another shipping method.

I solved. The products were in a warehouse, while the variations in another. With mass action I moved products and variants in a single warehouse, and I solved it.
It was not very intuitive solve the problem because the warehouse field appears only in the main product and not in the variants. However I solved

@Hikashop Team: This is a quick fix for the user, but I just stumbled on the same issue with a customer's shop. The underlying issue should be resolved or at least a warehouse-field added to the variants, so that people can at least correct such problems without having to do mass actions.