Under the weather

Precipitation being drawn at infinite distance when set to zero is incorrect behaviour. This is likely the consequence of a bad merge, but I don't care enough to check for certain.

(When I backported this to vanilla a while back, I don't know whether I also made the zero-value for that cvar turn the weather off or whether I kept it consistent with 2.1.whatever. If it turns out yalls need it too, let me know and I'll do it upstream.)