Treat "blank NPS" Differently Than "0 NPS" in the Global Client View

At the moment, clients who have no NPS data are ranked as though they have a score of 0. When organizing the view by NPS, this means we see all the positive values, and then a whole bunch of blanks before you can see the 0 and negative values at the very bottom. Logically it would be great to have blank NPS treated as though it were a value of -101, so it doesn't appear in the middle of clients who have actual NPS scores