Describe the bug
Players cannot place backpacks into the combine backpack, even though I turn on backpacks.nest. Although I don't want players to put their backpacks in other backpacks (ex: a large backpack)

To Reproduce
Steps to reproduce the behavior:

1. Open a combine backpack.
2. Try to place a combine backpack into combine backpack.
3. Doesn't proceed and puts it straight back into the players inventory

Expected behavior
What I expect to happen is that, players can put either a small, large or even an ender backpack into a combine backpack.

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

Version info
Spigot 1.16.5

You put backpacks in the combined backpack by combining the desired backpack with the combined backpack in a crafting grid.