Describe the bug
Items can be duplicated in the Crafting UI when closing it instead of actually crafting the item. This occurs in all worlds.

To Reproduce

1. Be in Survival mode
2. Open your inventory and place items in the crafting slots to craft an item (like a torch or to dye a Shulker box)
3. DO NOT CRAFT THE ACTUAL ITEM
4. Close your inventory
5. The items that were in the crafting slots will now be back in your inventory
6. Re-open your inventory and you will see that you're able to take what you would have crafted out of the craft slot (while the items needed to craft the item at hand remain unused and in your inventory)

Expected behavior
For this to not be possible at all

Pastebin
Exception in console:
https://pastebin.com/bTiHLej6

Please complete the following information:

• Resource Version and Build Number: v5.2.2-RELEASE-b734
• Server Version: git-Paper-762 (MC: 1.16.5)

Confirmed as a bug, the issue is now resolved in the latest snapshot.
Link; https://ci.craftationgaming.com/job/ItemJoin/764/
Remember to remove your old ItemJoin.jar file
Let me know!~

Thanks a bunch!

I've updated the plugin and everything is working as intended once more.