Minecraft Version: 1.16.2
Carpet Version: 1.4.9
this is crash report https://paste.ubuntu.com/p/M6Gn2SVZBV/

Are you able to reproduce this in MC 1.16.3-RC1 and Carpet version 1.4.10? If so, can you please post the corresponding logs here? Also include steps to reproduce if possible.

It is on playing the server crashes suddenly, maybe reproduce it not easy, I will try it.

Have seen that in the past, but wasn't easy to reproduce. Easy to prevent, but I would want to be able to fix the logic rather than patch the NPE.

So any detail is welcome

• any specific moment it crashes (start of the server), or just randomly
• I assume spawn tracking must be on
• is it for specific mob, what are the conditions of the area (any specific mobs not spawning etc.)

server is up 3 days, I think it is randomly.
I think this seed maybe useful level-seed=32932572289994442.
when before crash, only my friend in game, sayed he find the parrot, then server crash.

Ok, that explains it and I know exactly what is going on. Good bug tracking skills, @altrisi

Could reproduce it in the given seed and given position (x=-2474.67, y=68.25, z=377.22), while in a tickwarp to make it occur sooner (to make it even faster, have a repeating command block running /kill @e[type=!player] to free the mobcaps).
May it be related to ocelots, since they spawn with the hostile conditions in jungles (the area is a jungle)?

It seems to be directly related to Ocelots!
Testing in a superflat world, jungle biome, y>63, daytime (only ocelots can spawn because of full passive mobcap), instant crash after starting spawn tracking.
Preset: minecraft:bedrock,62*minecraft:dirt,minecraft:grass_block;minecraft:jungle
Full log: https://hastebin.com/vedoraxane.sql
(in 1.4.9)

Is it just related to Ocelots or does the crash also affect cats naturally spawning in villages?

@gnembon Yes, the crash happens only after starting the /spawn tracking (instantly in the flat world).
@James103 No, it doesn't happen with village cats, just tested.

Can reproduce in Carpet mod 1.4.0 and MC 1.16.1, so either a regression or the bug has been there for more than a few weeks as of now. Log and crash report (version info included)

Relates to (is duplicated by) #399 and #402