[BUG] _optionals error reported after exiting the bot.

[Nullably]

Describe the bug
A user reported the followings:

When exiting the Docker version, I get the following error. Does anyone else? AttributeError: 'NoneType' object has no attribute '_optionals' it also totally mangles the UI of the shell. I have to reset it for it to be usable again.
not a huge deal, but an annoyance... wondering if I'm the only one

From @mifeng

when i exit the client, i sometimes get this error (installed from source). has anyone else seen this/

After some investigation, this can happen when user accidentally hit space bar on the hummingbot input (without issue any command) then exit the app

Steps To Reproduce
Hit space bar on the hummingbot input (without issue any command) then exit the app