bug with 2.15.39 fixed with 2.15.42: good job but no reg test

[Frédéric Bron]

The following snippet does not give 1/32 notes grouped together as
expected with 2.15.39:

\new Staff {
        \clef treble \key bf \major     \time 3/4
        \set Score.beamExceptions = #'(
                ( end .
                        (
                                ( (1 . 32) . (4 4 4 4 4 4) )
                        )
                )
        )
        \repeat unfold 24 c'32
}

I just checked with latested 2.15.42 (fresh git pull) and it works as expected.
Thanks!
I do not see this tested in our regtests. Could we add it?

Frédéric