Error when we disable "billing address step" in nopcommerce 4.1

Hello,

I have found a bug in nopcommerce 4.10 by doing following steps.

step 1) do disable "billing address step" and disable "one page checkout".

step 2) delete all addresses from my account section.

step 3) now add any product to cart and do proceed to checkout , it is throwing error "value cannot be null".

Thanks a lot! We'll check it - https://github.com/nopSolutions/nopCommerce/issues/3556

Done. Please see this commit for more details.