I wasnt on the server at the time of this crash, but the player that was on said that a crimson moon started and then he got kicked with a stack overflow message.
Crash Log: https://hastebin.com/nafagesopa.sql

Played single player. The crimson night started, everything went red and text notified me of this. After about a second or two I received the crash. Seems to be the same problem: https://pastebin.com/SvfKq7jK

Seems to be an issue with some biomes not having valid mobs to spawn. My IDE was warning me about the exact line that is crashing in your log, so I'm wrapping it in a null check for 1.2.2 and hoping the issue is fixed. Let me know if you still see it.