Add "no label" category

[andiandi13]

I'm currently sorting my notes by assigning labels, and because I have many notes, I realized it was hard to find those which don't have labels in order to assign one. I'm using the "Hide Labels in Overview" option, but even when i disabled it, I have to scroll through a lot of notes.

It'd be nice to have an "Unlabeled" or "No Labels" category in the navigation panel :

Also this could appear on the search bar filters.