Inventory bug that causes items to be constantly shuffled

Creative mode inventory bug that causes the player to constantly shuffle through their inventory, also causing a lot of client lag.

Steps to reproduce:

1. Set player game mode to Creative mode
2. Get half full inventory of items of a same material
3. Spam click one of the item stacks in the inventory with another item stack

This doesn't always work, so might need a few tries before it happens.