I have a client that tried to add the product to the Shopping Cart and it doesn't Estimate Shipping & Taxes, so i went to error log and theres something wrong with default wt based for 1.3.4 using php 8 +
existing default code set cost = '' instead of 0
php 8 does not allow string to be summed with integer
so the fix should be cost = 0;
line 55 in the code should be 0