In the case where there is no next item, the progress will not get updated, so we'll essentially skip one element from filling the progress bar further. In the future we may/will want to not hide the notification upon completion, so this will look better in such scenarios.
E.g. because DrawableSpinner doesn't (currently) create an overlay, SelectionBox was being constructed with 0 hitobjects and then calculating a non-finite size for itself.