problem with beamed graces and midi output

[scott snyder]

hi -

This is concerning lily 1.3.121, on a linux/i86 system compiled with
redhat gcc 2.96.

I find that if i try to use beamed grace notes with midi output turned
on, lily gives me some annoying warnings.  For example, this input:

-------------------------------------------------------
\score{
    \notes\relative c''{
      a4 b \grace {[b8 c]} d4 e
    }
  \paper {}
  \midi {
    \tempo 4=120;
  }
}
-------------------------------------------------------

gives the warnings

Interpreting music...
grace.ly:3:20: warning: Junking request: `Span_req':
      a4 b \grace {[
                    b8 c]} d4 e

grace.ly:3:25: warning: Junking request: `Span_req':
      a4 b \grace {[b8 c]
                         } d4 e



I can make these warnings go away by adding a Swallow_performer to the
grace performer group, as in this example:

-------------------------------------------------------
\score{
    \notes\relative c''{
      a4 b \grace {[b8 c]} d4 e
    }
  \paper {}
  \midi {
    \tempo 4=120;
    \translator {
      \type "Grace_performer_group";
      \name Grace;
      \consists "Swallow_performer";
    }
  }
}
-------------------------------------------------------

But perhaps this should be done in performer.ly?

thanks,
sss