Furnace recipes causing issues with Slimefun4

[LcyDev]

What happened?

When you use an Enhanced Furnace of Slimefun4 and try to use recipes made in Custom Crafting, everything's fine until the last item gets smelted.

Once that happens, an error will pop up in the console.

How can the bug be reproduced?

1. Install Slimefun4.
2. Make a CC furnace recipe.
3. /sf give <player> ENHANCED_FURNACE
4. Try smelting the custom recipe in it.
5. Check the console for errors.

Expected Behaviour?

This shouldn't happen

Plugin version

CustomCrafting-4.16.5.1 - WolfyUtils-4.16.9.6

Server software

Purpur (1.19.3) b1900

Relevant log output

https://paste.gg/p/ConaII_/ba285dbaa2654c33a3544a0e8b714ba9

https://paste.gg/p/ConaII_/ce0b4a7588a34a96a7b233f099e54ec7

Submit issue

• [X] read the Wiki and especially the FaQ, and made sure there is no fix to your issue,
• [X] searched for and ensured there isn't already an open issue regarding this,
• [X] are running the latest version of your server software (Spigot, Paper, etc.), and plugins (WolfyUtilities, CustomCrafting).

[LcyDev]

https://github.com/Slimefun/Slimefun4/issues/3741

[J3fftw1]

This issue is fixed in https://github.com/Slimefun/Slimefun4/pull/3756 For some reason CustomCrafting adds a null item. We still should have checked for it in the first place but still weird a null item is being added.

[WolfyScript]

This issue is fixed in Slimefun/Slimefun4#3756 For some reason CustomCrafting adds a null item. We still should have checked for it in the first place but still weird a null item is being added.

Yeah, I don't know why it happens, I guess it can be null by desing (at least that's what the API says). I had to also check if the smelting item is null, because another plugin caused the same issue before.
https://github.com/WolfyScript/CustomCrafting/blob/73bebaa50537ac36ff0bd492375eb067d9014242/src/main/java/me/wolfyscript/customcrafting/utils/cooking/SmeltAPIAdapter.java#L92

[J3fftw1]

im guessing your check happens later then we check the smelting for some reason. Might also just be spigot jank