[2.0.10] maximum_productivity can be negative

[PennyJim]

Setting a recipe to have a maximum_productivity a negative value will not error on startup.

Playing around with it, all it seems to do is make the productivity value underflow, and proportionally lower. It seems to have no negative consequences besides displaying this underflow to the user. It neither produces extra products, or even reduce product produced.

You can also set it to 0, which can be considered invalid behavior, but there are be arguments for keeping that.

The solution is to limit the range greater than (or equal to?) zero

[boskid]

Thanks for the report. For 2.0.11 i made it only accept values >= 0.