Command blocks go blank once you exit the command menu.

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Command blocks go blank once you exit the command menu.

What I expected to happen was...:
I wanted to use a command block.

What actually happened was...:
I tried to execute said command only to find the block was blank.

Steps to Reproduce:
1. Put a command in a command block
2. Leave the command menu.
3. Re-enter the command block to find it empty and go insane.