Issue Description:

The getSubItems method in MCItemDefinition can sometimes throw a null pointer exception.
I have tried some tests to find the source of the issue, but it seems kind of inconsistent.
My test script.

What happens:

It will sometimes throw this exception, which will cause the script to crash.

What you expected to happen:

The behavior to be consistent, or catch the null pointer.

Script used (Please Pastebin or gist your script, posting an unpasted or ungist'd script will automatically close this issue):

https://pastebin.com/57DPyjUZ

crafttweaker.log file (Please Pastebin or gist your file, posting an unpasted or ungist'd file will automatically close this issue):

Log output from test script

Affected Versions (Do not use "latest"):

• Minecraft: 1.12.2
• Forge: 14.23.4.2756
• Crafttweaker: 4.1.9
• Using a server: No
• If yes, does the client have the exact same scripts?

Your most recent log file where the issue was present:

My entire log file is 165k lines long, but I can find a way to post it if needed.

I'll assign.this to me, not sure when I will be able to actually look into it.