If you use an consumable Usable with quantity 1, the quantity is then decremented to zero and the stack is auto-removed by the InventoryController logic. The ViewInventoryAction does not detect this and then tries to view that stack index, thus causing a crash.
If you use an consumable Usable with quantity 1, the quantity is then decremented to zero and the stack is auto-removed by the InventoryController logic. The ViewInventoryAction does not detect this and then tries to view that stack index, thus causing a crash.