Issue Description:

When you open a Backpack (in my example I used Diamond Backpacks (Storage Emphasis)) and Shift + right click another Backpack in your inventory, it’s got moved into the opened backpack. No matter if there is Inventory in the moved Backpack or not. This basically creates an almost infinite Inventory.

What you expected to happen:

Backpacks cant be placed into another packpacks. Or at least not if they already hold content.

Steps to reproduce (important):

1. Create 2 Sorage Emphasis Diamond Packpacks
2. Open 1 Backpack
3. LShift + Rightclick the second Backpack

Affected Versions (Do not use "latest"):

• IronBackpacks: 1.12.2-3.0.8-12
• Minecraft: 1.12.2
• Forge: 14.23.5.2838