Mobs fall out of minecarts

Whenever a mob is attacked into a minecart (they get hit by player and knocked into a minecart) and the player clicks on the minecart to make it disappear, the minecart disappears (as it should) but the mob falls through the ground. They fall through the block that is directly beneath them and land on the one below it.

*What I expected to happen was the mob would land on the block directly beneath it.

*What actually happened was the mob fell through the block directly beneath and landed on the one below the top layer

Steps to Reproduce:
1. Place a minecart on a track
2. Spawn a mob in creative mode
3. Hit the mob into the minecart
4. Push the minecart in a direction
5. Once it has stopped, hit the minecart to make it disappear
6. Then the mob should fall through the ground