Could not use command blocks when a LAN server was open.

I clicked a command block (on creative mode with cheats enabled), and I expected it to open into the command block menu where you can type the command.

However, nothing happened. It acted like clicking any other block with an open hand. If clicked with a block the block will not be placed.

Steps to Reproduce:
1. Open a Minecraft world to LAN (Other players do not have to be on)
2. Collect a command block with /give @p command_block
3. Try to operate the command block