Description of the issue:

I tried firing the railgun with my offhand without any item on my main hand. After releasing the charge, the multiplayer server crashes.

Crashlog:

https://pastebin.com/CXnCdb7p

Versions & Modlist

IE Version: ImmersiveEngineering-1.16.5-4.2.1-131.jar
Forge: forge-36.0.15
Modpack: Valhelsia 3-3.1.8a https://www.curseforge.com/minecraft/modpacks/valhelsia-3

Edit by @malte0811: Fixed links