<None> Category option for NUnit runner?

I've started using categories to set aside problematic tests (long
running, heavy fixture, what-have-you) ... it'd be nice if there was an
easy way in the Category view of the R# NUnit runner to see all the
tests not in any category at all, so I could run every test that's not
in a category at all yet. Currently, I only see an (plus each specific category). It's a lot of tests to have to go back and set them to my own custom category to create my own ]]> group.