Detect when in system menu...

[Phinix]

I have an addon I want to ignore callbacks when the game's system menu is open (the one when you hit Escape, where you log off).

I was going to set a boolean when in the menu, but I need to be able to reliable check specifically when the main system menu is open, and when it is closed in order to toggle it.

I was looking through SCENE_MANAGER but so far I am not finding it...