Issue Description:

Backpack must be opened once via a normal right click in a hotbar slot before it can be used correctly. This is obviously not ideal.

What happens:

Backpack doesn't operate correctly. Deletes/dupes items, etc.

What you expected to happen:

Normal functionality like other backpacks.

Steps to reproduce (important):

1. Make any backpack, and don't open it.
2. Right click it from an inventory.
3. Watch as it doesn't update contents correctly.
   ...

Affected Versions (Do not use "latest"):

• IronBackpacks: 1.10-all

Should be solved as of rewrite.