Describe the bug
a backpack's inventory turns to empty small backpacks inventory when wearing backpack and clicking a linked chest with a backpack key

To Reproduce
Steps to reproduce the behavior:

1. link a linked backpack to a chest
2. put on backpack
3. click linked chest with back pack key
4. open backpack

Expected behavior
nothing changes

Version info
backpack version:
Version: 2021.1.1
Git Commit: 8bdd12b
Git Build: 219
Download Page: https://dev.bukkit.org/projects/backpack-item

spigot version 1.17.1

full version command output:
This server is running CraftBukkit version 3258-Spigot-dc75aca-960f310 (MC: 1.17.1) (Implementing API version 1.17.1-R0.1-SNAPSHOT)
You are running the latest version

Additional context
works with small and large backpack deletes all items in backpack

@drew6017
sorry i was unclear there i meant a normal small or large backpack
and i did slightly more testing:

1 link linked backpack to chest
2 put on linked backpack
3 open linked backpack
4 put on normal backpack(small or large)
5 click on linked chest
6 open normal backpack

a demonstration
examle.zip

"2. put on backpack" wut? ma dude. you click the chest while holding the backpack in your hand to link it. then you put it on. then you hold bp key, then you use key and it opens the backpack.