Making Sync's destructor virtual (to prevent creation of Sync object)
diff --git a/model/sync-leaf.cc b/model/sync-leaf.cc
index 6ff48bc..6480480 100644
--- a/model/sync-leaf.cc
+++ b/model/sync-leaf.cc
@@ -30,6 +30,10 @@
 {
 }
 
+Leaf::~Leaf ()
+{
+}
+
 void
 Leaf::setSeq (const SeqNo &seq)
 {