[EXAMPLE] Stored items are dissappearing.

[Seppe Volkaerts]

• Spigot version: Spigot 1.8.3
• ItemBags version: 1.0.0-SNAPSHOT
• Describe your problem: My items dissapear after closing the inventory.
• What caused your problem: I try to add a item to inventory by using shift click and when I close and reopen the inventory it is gone.