message: correctly derive enablelogging from template parameter
diff: @@ -584,7 +584,7 @@ public:
  * class.
  */
  template <typename ConcreteLoggable, typename PolymorphicBase = Loggable>
  -class EnableLogging : public Loggable {
  +class EnableLogging : public PolymorphicBase {
  public:
  void add_logger(std::shared_ptr<const Logger> logger) override
  {
  