segfault in grob.cc

[John Galbraith]

With lilypond 1.4, I get a segfault in item.cc due to a NULL pointer
passed in from grob.cc at line 372.

Line_of_score * line
  = dynamic_cast<Line_of_score*> (unsmob_grob (criterion));
if (sc->line_l () != line)
  {
    sc = sc->find_broken_piece (line);
  }


Basically, I think the dynamic_cast is failing and returning NULL.  I have
no idea what part of my input deck actually causes the error, but I have
only triggered it with at least two parts enabled in a very complex
orchestral score.  Smaller segments do not trip the bug, and single parts
do not trip the bug, apparently.

If I disable the call to find_broken_piece(), then it crashes later at
item.cc, line 57

Line_of_score *
Item::line_l () const
{
  Grob *g = parent_l (X_AXIS);
  return g ?  g->line_l () : 0;
}

I have no idea if this is related to the first crash or not.  However, I never
get this crash without hitting the other one first.

I am using Redhat 6.0 (yeah, what a slacker, I know)
GNU LilyPond 1.4.0
gcc version 2.95.2 19991024 (release)
Linux debussy 2.2.5-22 #1 Wed Jun 2 09:17:03 EDT 1999 i686 unknown

John