Avoiding a layout lock on Region::empty.

src/db/db/dbOriginalLayerRegion.cc

@@ -330,7 +330,11 @@ OriginalLayerRegion::begin_merged_iter () const
 bool
 OriginalLayerRegion::empty () const
 {
-  return m_iter.at_end ();
+  //  NOTE: we should to make sure the iterator isn't validated as this would spoil the usability or OriginalLayerRegion upon
+  //  layout changes
+  db::RecursiveShapeIterator iter = m_iter;
+
+  return iter.at_end ();
 }
 
 bool