This started occurring after version 1.4.2 I think? The main culprit mod is Luki's Ancient Cities thought I can't recreate it on a fresh instance because you need quite a few mods present for the bug to occur. Maybe a mod that uses Lithostiched as a dependency and tries to modify ancient cities? Anyways, this seems like a bug in Lithostiched itself where it doesn't handle null data gracefully, though that's just my speculation.

See log: https://mclo.gs/iZp2DVX

Updated with recent info. Still trying to recreate this on a fresh instance without hundreds of mods. But, let me know if you have any ideas.

Closing as invalid, not an issue with Lithostiched. Apologies.