Stats tree seems to work properly, including pruning of "empty" leaves
diff --git a/utils/load-stats-face.cc b/utils/load-stats-face.cc
index 834004a..2e66197 100644
--- a/utils/load-stats-face.cc
+++ b/utils/load-stats-face.cc
@@ -58,6 +58,12 @@
   return *this;
 }
 
+bool
+LoadStatsFace::IsZero () const
+{
+  return m_count.IsZero () && m_satisfied.IsZero () && m_unsatisfied.IsZero ();
+}
+
 std::ostream &
 operator << (std::ostream &os, const LoadStatsFace &stats)
 {