Description of the issue:

If OptiFine is installed along with Immersive Engineering and you decide to turn on/off shaders, the game will crash.
Changing any values in immersiveengineering-client.toml related to rendering doesn't make any difference.
You can reproduce this with built-in internal OptiFine shader, as well as any other external shader.

Crashlog:

Crashlogs come in two variants, which slightly differ.

1. When shaders are turned off (something -> off): https://pastebin.com/NgdxDnkx
2. When shaders are turned on (off -> something): https://pastebin.com/yVMPbDM2

Versions & Modlist

Forge 36.0.21
OptiFine HD U G7 pre8
Immersive Engineering 4.2.1 131

Optifine is not supported.