rose edit: rosie go: no jumping focus on valuewidget errors

If you correct or cause an error while typing in values in the
`rosie go` new suite wizard, the focus will jump. This fixes
the behaviour of the particular `rosie go` page in `rose edit`.

(The code comes from one of the other classes in the module).

@arjclark, please review.
I think it'd be better to write `r += 1`