Minecraft Version : 1.12.2
Forge Version: 14.23.5.2855 (Latest when submitting this report)

Issue:

When adding a recipe that involves the Arc Furnace through JEI that DOESN'T have a slag output, game crashes.

Mods:

• JustEnoughCalculation 1.12.2 - 3.2.6
• JustEnoughItems 1.12.2 - 4.16.1.301
• Immersive Engineering - 0.12 - 98

Steps to reproduce:

1. Open crafting calculator and search on JEI an item that involves the Arc Furnace (ex. Iron ingot from iron grit)
2. Press the "+" to "Move Items" on a recipe that doesn't have a slag output (ex. Iron ingot from iron grit)
3. Crashes with exception "IllegalArgumentException: Stack can not be invalid!"

Image related:

I'm attatching the crash Log hoping it helps:
crash-2021-08-09_14.39.54-client.txt

Thanks for report
I'll have it fixed soon