Inventory won't clear in creative mode

When entering the command /clear after shift-clicking the "Destroy Item" button in the creative inventory, the command will give out an error even if you have something in your inventory.

How to reproduce:

1. Join a server or a singleplayer world.
2. Make sure you are in creative and operator
3. Shift-click the "Destroy item"-button in the creative inventory.
4. The items in your inventory won't clear.
5. Future /clear commands will output an error.
6. When the inventory changes (new items are added or removed), the /clear command will work again