v0.2.55..v0.2.56 changeset IsSortedVisitor.h

diff --git a/hoot-core/src/main/cpp/hoot/core/visitors/IsSortedVisitor.h b/hoot-core/src/main/cpp/hoot/core/visitors/IsSortedVisitor.h
index a2a106a..083e3e7 100644
--- a/hoot-core/src/main/cpp/hoot/core/visitors/IsSortedVisitor.h
+++ b/hoot-core/src/main/cpp/hoot/core/visitors/IsSortedVisitor.h
@@ -49,6 +49,7 @@ public:
   static std::string className() { return "hoot::IsSortedVisitor"; }
 
   IsSortedVisitor();
+  virtual ~IsSortedVisitor() = default;
 
   virtual void visit(const ConstElementPtr& e);