update / fix the underground rivers datapack

https://www.planetminecraft.com/data-pack/underground-rivers-tech-demo/ This datapack by Apollo looks really cool, but unfortunately it's broken, although I don't think it should be necessarily that hard to fix, as there's only one simple error that pops up in the console: "Caused by: java.lang.RuntimeException: No key has_precipitation in MapLike[{"carvers":{"air":(bunch of stuff)". How can I fix that?