robustness fix: allow Music_wrapper with null child. Fixes #177

diff --git a/lily/music-wrapper-iterator.cc b/lily/music-wrapper-iterator.cc
index c50a64c7c10f97082658bdaff72fada615b789b1..30c9ec7f19e43beaa1c2f6cdd84f063d251dddc7 100644 (file)
--- a/lily/music-wrapper-iterator.cc
+++ b/lily/music-wrapper-iterator.cc
@@ -17,7 +17,8 @@ Music_wrapper_iterator::Music_wrapper_iterator ()
 void
 Music_wrapper_iterator::do_quit ()
 {
-  child_iter_->quit ();
+  if (child_iter_)
+    child_iter_->quit ();
 }
 
 void
@@ -39,7 +40,9 @@ Music_wrapper_iterator::construct_children ()
 {
   Music *my_music = get_music ();
   Music *child = unsmob_music (my_music->get_property ("element"));
-  child_iter_ = unsmob_iterator (get_iterator (child));
+  child_iter_ = (child)
+    ? unsmob_iterator (get_iterator (child))
+    : 0;
 }
 
 bool
@@ -51,13 +54,17 @@ Music_wrapper_iterator::ok () const
 void
 Music_wrapper_iterator::process (Moment m)
 {
-  child_iter_->process (m);
+  if (child_iter_)
+    child_iter_->process (m);
 }
 
 Moment
 Music_wrapper_iterator::pending_moment () const
 {
-  return child_iter_->pending_moment ();
+  if (child_iter_)
+    return child_iter_->pending_moment ();
+  else
+    return Music_iterator::pending_moment ();
 }
 
 IMPLEMENT_CTOR_CALLBACK (Music_wrapper_iterator);
@@ -65,5 +72,5 @@ IMPLEMENT_CTOR_CALLBACK (Music_wrapper_iterator);
 bool
 Music_wrapper_iterator::run_always () const
 {
-  return child_iter_->run_always ();
+  return (child_iter_ &&  child_iter_->run_always ());
 }

diff --git a/lily/music-wrapper.cc b/lily/music-wrapper.cc
index 051187a8a4215f6d3feb6e6e8cd2283526448d70..5f141c0c910478a4dbf4e8a8485971224fe55e94 100644 (file)
--- a/lily/music-wrapper.cc
+++ b/lily/music-wrapper.cc
@@ -16,7 +16,10 @@ Music_wrapper::start_callback (SCM m)
 {
   Music *me = unsmob_music (m);
   Music *elt = unsmob_music (me->get_property ("element"));
-  return elt->start_mom ().smobbed_copy ();
+  if (elt)
+    return elt->start_mom ().smobbed_copy ();
+  else
+    return Moment ().smobbed_copy ();
 }
 
 MAKE_SCHEME_CALLBACK (Music_wrapper, length_callback, 1);