Upon re-entering an enchantment table in creative when having thrown something in the ground, the thrown item is duplicated into the inventory again. The other item which was thrown on the ground can still be picked up, therefore clogging up the inventory. Throwing the item must be done by entering the survival inventory, hovering over the item and then pressing the drop key.
This was only tested in 14w31a and 14w32a, and works in both versions.

This is me demonstrating the glitch: https://www.youtube.com/watch?v=NMjRf9gO18A&feature=youtu.be

What I expected to happen was...:
The item should not be duplicated.

What actually happened was...:
A copy of the item on the ground is duplicated into the inventory.

Steps to Reproduce:
1. Go into creative mode
2. Put any item into your survival inventory
(2.1 Enter the enchantment table GUI, and exit it again - [It is not sure if this is necessary])
3. Enter your survival inventory, hover over the item from step 2, and press the drop key.
4. Enter the enchantment table GUI again. The item, even though it was thrown out of the inventory, is now in the same slot again.
5. Pick up the item you threw away on the ground. You will now see: The item was duplicated. Both items behave absolutely normal and can be used without disappearing.