When a zombie picks up an item and dies without the player killing it, it wont drop the item it picked up.

Example, if you have a mob farm that kills by fall damage and a zombie picks up an item they wont drop it when they die.

What I expected to happen was...:
I expected a zombie to drop the items it had picked up without me having to kill it my self.

What actually happened was...:
When a zombie dies of fall damage, and probably other deaths that don't include interaction with the player, it wont drop items that it has picked up off the ground. Along with this zombies can pick up items moments before dying of fall damage in the same spot the items they picked up were sitting.

Steps to Reproduce:
1. Make various mobs fall into the same spot from a high enough height to kill them by fall damage.
2. let mob drops gather up at the bottom
3. watch as zombies fall, the will sometimes be able to pick up the items where they're dying at right before they hit the ground, when they do they wont drop the item they picked up.