* lily/break-substitution.cc (substitute_mutable_property_alist):

[lilypond.git] / lily / break-substitution.cc

diff --git a/lily/break-substitution.cc b/lily/break-substitution.cc
index 2238f4495751a7f87a3946502670258d52dbfd3e..3ccc16c09063bbc80beeb2b0dd8059280673ed32 100644 (file)
--- a/lily/break-substitution.cc
+++ b/lily/break-substitution.cc
@@ -478,10 +478,17 @@ substitute_mutable_property_alist (SCM alist)
       else
        val = do_break_substitution (val);
 
-      *tail = scm_cons (scm_cons (sym, val), SCM_EOL);
-      tail = SCM_CDRLOC (*tail);
-    }
 
+      if (val != SCM_UNDEFINED)
+       {
+         /*
+           for ly:grob? properties, SCM_UNDEFINED could leak out
+           through ly:grob-property
+          */
+         *tail = scm_cons (scm_cons (sym, val), SCM_EOL);
+         tail = SCM_CDRLOC (*tail);
+       }
+    }
   return l;
 }