Steps to reproduce:

Build a portal and enter the nether. The ore spawn crashes. I thought I had disabled it. I'm not able to join the world anymore although I deleted the nether in saves folder.

Versions:

• Minecraft: 1.12.2
• Forge: 2836
• McJtyLib: 3.5.0
• RFTools: 7.70

Relevant logs, if any:
crash-2019-05-04_16.12.57-server.txt
crash-2019-05-04_16.39.00-server.txt
crash-2019-05-04_16.58.46-server.txt

Here are the configs:
https://pastebin.com/hPR6JtdU RFTools Dimensions
https://pastebin.com/L8mEGVNk RFTools

I fixed the off-by-one error that's the real cause of the crash. It will take effect in the next version of RFTools. However, you shouldn't have been hitting that; the only reason that you were is that you're using an outdated config file format. Delete your config and let it regenerate (then restore your settings to it).

I can confirm. I graded down to the version before 27 April and this solved the crash,