Comment 14 for bug 1785314

So
bindings:
  "": undefined

Certainly seems like something that we really don't want to support. And if you have applications being deployed into containers on machines where there *are* multiple spaces, Juju has no idea where to put the application (and what spaces route from the host machine into the containers).
So we can certainly put a safety in to prevent you from specifying this, but really where do you *want* those applications to be. I don't think you want them to be undefined in the containers