Screen behind chat goes all black (instead of showing the world) when you type / to start a command

The screen became black when u try to use commands

rplatham edit:
It looks like the autocomplete command options are forcing the background solid black. If cheats are disabled in the world, typing / does not start a command and does NOT shade the window all black.

When you open the chat window, you can still see the world through the background. However, when you type a / to start a command the window shading goes all black so you cannot see the world any more. I expected that you would still be able to see the world.