Fix segfault in Rest_collision_engraver if there is no NoteColumn.

diff --git a/lily/rest-collision-engraver.cc b/lily/rest-collision-engraver.cc
index 7156409d51dd0adb7140b9171d3babef6255472d..4720368c909c3fd5da2a5838c2288e0bce675289 100644 (file)
--- a/lily/rest-collision-engraver.cc
+++ b/lily/rest-collision-engraver.cc
@@ -10,6 +10,7 @@
 
 #include "duration.hh"
 #include "engraver.hh"
+#include "international.hh"
 #include "item.hh"
 #include "moment.hh"
 #include "note-column.hh"
@@ -53,6 +54,11 @@ Rest_collision_engraver::process_acknowledged ()
       if (Rhythmic_head::has_interface (g) && (*m) > now)
        {
          Grob *column = g->get_parent (X_AXIS);
+         if (!column)
+           {
+             g->warning (_ ("rhythmic head is not part of a rhythmic column"));
+             continue;
+           }
 
          // Only include rests that start now. Include notes that started any time.
          Paper_column *paper_column = dynamic_cast<Item*> (column)->get_column ();