How can I delete blank viewpoint boxes?

 When I press pan & tilt, at the bottom of the screen I seem to have ended up with a blank box first with a + in it, then a view I want to keep, then another 2 blank boxes then another view I want to keep, then more blank boxes. So I have 2 views I want to keep and quite a few blank boxes I don't want. (They all have a + in them) Can anyone advise?