Option to hide new sidebar in Firefox

[ChiefArug]

I opened one of my web apps today and the new sidebar popped up. (the address bar is a seperate issue, #320)

I did manage to disable it, but it required setting the sidebar button to 'Show and hide sidebar' then turning on the address bar, clicking the sidebar button in the address bar to hide it, then turning off the address bar again.
Never mind, it came back after a restart... grrrr

Would be nice if this was automatic, either tied to the address bar toggle or with a new toggle.

It also seems like this is being rolled out, as only one of my profiles has it.