Minecart falling through the ground when not on rails.

I expected that the minecart should just stay on the surface as it has done in previous versions on minecraft when not on a rail.

Instead the minecart just fell through one block of the ground. It is though still moveable but is just placed underground.

1. Place a rail somewhere
2. Place the minecart onto the rail
3. Then destroy the rail and the bug should appear