shortest: fails to work on `nullable<lat<lal>>, b`
The problem appears to be that the label set multiplication of the corresponding wordset does not accept the letters
from nullable<lat<lal>>
.
Labelset: nullable<lat<lal>>
Wordset: lat<wordset>
.
All this should disappear with Sarasvati's changes for 2.6, so I am not going to spend time on this now.