Pastebin: https://pastebin.com/X57RAHFB

Forge 2847
MC 1.12
ThaumicAugmentation-1.12.2-1.1.10.jar

I remembered the cause a bit better and updated the subject.

I pasted the error log here because it appears the error was in a Thaumic Aug call..

This specific crash seems to be caused by Optifine creating a chunk with a null world, which is really not supposed to be null. In this case it's easy enough to guard against on my end, but I can't always guarantee compatibility with every crazy thing Optifine tries to do.

If you take a look at the crash report you sent me, while my mod is at the very top, a few lines down is Optifine code (something to do with shaders?). I used that to do some investigation to find out it was indeed Optifine's fault. I didn't read too far into it, but it's creating a chunk instance to pass into something. I'm working on something right now, and after I test it I'll be releasing an update that should fix this issue.
As for reporting it to Optifine, you can if you want - that world field is not marked as being Nullable in the event so I still don't think this was my fault, but maybe I was just being a bit too idealistic in my assumptions that these things wouldn't happen.

The update should be available here.

Thank you sir.