Bare modpack with Optifine (tested both E4 and E5) crash on launch
https://paste.ee/p/5J53J

I couldn't reproduce this issue with OptiFine 1.13 HD U E4, 1.13.2 HD U E5 or 1.13.2 HD U E6 pre2.

I can't look at OptiFine's source code to figure out what's wrong, but have you tried disabling all resource packs and shaders?

I figured out what it was. I had a WIP sky resource pack: https://github.com/ScottoMotto/ScottoMotto-Sky-Universal

I was trying out different colormaps and trying hide them by changing the extension to .bak... Mac sometimes fools you and doesn't actually change the extension. So it was .bak.png.

For some reason every Rift mod but yours didn't mind this and the sky worked fine. Interesting... but thanks for helping to figure this out and sorry to waste your time chasing shadows.

You can close this issue.