Describe the bug
A clear and concise description of what the bug is.
Place an item to inventory crafting slot, will show red error message
ceh 2.4.2
paper 457 1.16.5
To Reproduce
Steps to reproduce the behavior:

1. put item to crafting slot
2. red error message shows in console
   

Show console logs
Please show the startup logs and logs of the error itself. Pastebin.com is a nice site that allows you to paste large console errors.

[optional] add items.yml and recipes.yml
To reproduce the bug, it could be helpful to see the items and recipes that you're using. Decide yourself if you want to provide this.

items.txt
recipes.txt

I have not closed this issue, even though it seems to be fixed. Sorry for not handling your issue professionally.

First of all, thanks for reporting this bug.

I would also like to know if this causes any critical issues like duping. If that's the case I am going to fix this immediately.

no major problem, just error message appear so far