https://paste.dimdev.org/nogupifele.mccrash

Any more information about this issue? When did this happen? Caused this a crash?

happened spontaneously, caused repeated crashes (suppressed by vanillafix but seemingly endlessly replicating) until reboot

And without vanillafix?
Oh and could you post a full log?

2019-01-08-2.log

There should only be one way of the buffer becoming null: when two threads work on the same memory address. That makes sense in this case, because the error is thrown in the packet decompressor thread here. I have synchronized the appropriate parts of the code.

Please re-test with build 111.