When giving a player an item in the same tick as a /clear command, the item is invisible until the player right clicks on a block.

Verification builds: Release_459200 (In full release of 1.2 as well)
Summary:
If you create commands that, within a single tick, first clear your inventory and then give you an item, that item will technically be in your inventory but will only appear AT ALL if you right click on a block with that hotbar slot selected.

Impact:
Here is an example of how this affects our particular project: https://youtu.be/Qszwrm5izDs

Steps to Reproduce:
Create an impulse command block with a chain command block coming off of it.
IMPULSE: /clear @p
CHAIN: /give @p snowball
Activate the impulse block.

Outcome:
The chat proclaims that the player's inventory has been cleared and then that an item has been given. However, it appears that nothing is in your inventory even when mousing over it. You can only get it to appear by selecting your first hotbar slot and right clicking on a block in the world.
https://youtu.be/sc4H4TRcZ-M

Expected Results:
To have nothing in the inventory except for a snowball in the first hotbar slot.

Screenshots/Videos attached: Yes, 2
https://youtu.be/sc4H4TRcZ-M
https://youtu.be/Qszwrm5izDs