Leash disappears if a mob tied to it dies

Describtion:
If a mob you have tied to a leash happens to die, the leash disapears with it.

What I expected to happen:
after the mob died, the leash would drop

What actually happened:
Leash disapeared

Steps to reproduse:
1. tie a mob to a leash (tested with a sheep only)
2. kill it by dragging it into a cactus or (tested) pulling it high up in the air and going back down. You can get down slowly (perhaps another issue?)
3. observe as the leash is nowhere to be found