When you put an anvil on a high place in creative mode, then converting world gamemode to survival mode before it falls touching the ground, it will crash the game.

*What I expected to happen was...:
The anvil will stay on the ground.

*What actually happened was...:
The anvil dropped with invisible texture, when picked up it will crash the game.

Steps to reproduce:

• Place an anvil on a high place.
• Return into main menu before the anvil falls touch the ground.
• Convert the world gamemode to survival.
• Open your world.
• The anvil will turn into invisible dropped item.
• Pick up the invisible item.