Spoilage recipes break total cost in shopping list

[Factoriac9]

• latest version of YAFC (2.15.0)

Using a recipe that is a result of spoilage breaks the "total cost of all objects" in the shopping list, probably due to not having any cost for the 'character' entity used for spoilage

To reproduce:

• Open YAFC with a vanilla space age project file
• Create a production sheet producing iron ore, with the recipe "iron bacteria spoiling"
• If desired, add further steps to make sure there are some other machines in the production sheet
• Open the shopping list from entity > shopping list
• The total cost of all objects shows as "¥-", regardless of the number of machines in the sheet
• Removing the spoilage recipe from the sheet will make the total cost of all objects show normally

I suggest the 'character' entity should have a cost of 0 when calculating total cost.

[lukaskollmer]

possibly related to #499