Re: Issue 1715 in lilypond: Ligature and ambitus cause segfault

[lilypond]

Comment #2 on issue 1715 by address@hidden: Ligature and ambitus  
cause segfault
http://code.google.com/p/lilypond/issues/detail?id=1715

This would seem to imply that we should ignore note-heads without an  
event-cause.  Perhaps in listen_ligature we should do

if (ev->get_cause ())
  {
    Direction d = to_dir.....
    ASSIGN_EVENT_ONCE ....
  }

so that events without a cause are never assigned.