[Numbered Workspaces] Don't wrap around when scrolling

[git-f0x]

It would better match the behavior of keyboard shortcuts for changing workspaces, since they don't return to workspace 1 when trying to go past the last workspace.
This would enable quickly going to the empty workspace on the end (in dynamic workspaces), and would behave somewhat better with touchpad scrolling.
And personally, I think it would feel nicer. :)