Steps to reproduce:

1. Go into a world with creative mode and cheats
2. Fly up above the world anywhere, any height
3. Use the following command: /setblock ~ ~ ~ minecraft:grass
4. Enjoy your floating grass. 

What happened:

The dead bush/grass is floating in the air.

What I expected to happen:

For the dead bush/grass to break and fall, or at least do that when the block updates.

 I should be able to get a screenshot on here soon...