Duplication Glitch in single player

Some days ago I saw a video which showed how to duplicate stuff in the newest version (0.50).
1. Place a block in a chest
2. Close the chest
3. Open the chest
4. Take the block out of the chest
5. Place the block
6. Press the middle button to exit the App (don't save)
7. Double tap the button and delete Minecraft PE from recently used Apps.