[Trinidad] selectOneChoice: Make "unselectedLabel" item go away after selection?

[Stephen Friedrich]

I like to show "Please choose" in a selectOneChoice as long as no
option has been selected, yet.
As soon as the user selects one of the items the label should vanish
from the list.
(autoSubmit is set and the selectOneChoice is partialTrigger for itself.)
It really doesn't make any sense to select "Please choose" from
the list after having already selected something for real.