[BUG] Crafting backpacks together reverts them to leather armor

[SlashLife]

Describe the bug
Crafting a backpack together with an incompatible backpack results in a leather tunic.

To Reproduce
Steps to reproduce the behavior:

1. Craft two large backpacks
2. Put both large backpacks together; the result shows as an ordinary leather tunic with name "Leather Tunic"
3. Craft the leather tunic
4. Equip the leather tunic
5. Attempt to open the backpack using the backpack key: Nothing happens

Expected behavior
Crafting incompatible backpacks together should not be possible.

Screenshots
If applicable, add screenshots to help explain your problem.

Version info
Spigot 1.20.1 (3871)
Backpacks 2022.1.8

Additional context
This also applies to, and was first experienced, when attempting to combine a tenth backpack into a Combined Backpack.