@ streim
Whilst this is a new option, which allows avast to be set in passive mode (on-demand only) if you have another AV installed. As far as I'm aware, it is off by default, so it shouldn't be an issue.
I would have thought that you can only tick that option if you have another resident AV installed. Not that I would ever want that, I'm still a strong believer in only one resident AV installed and for me this passive mode idea, stinks, I have avast and no other AV.