fix missing virtual destructor in PointSourcePanner

closes #56

Author: tomjnixon

src/common/point_source_panner.cpp

@@ -224,6 +224,8 @@ namespace ear {
     return ret + 1;
   }
 
+  PointSourcePanner::~PointSourcePanner() {}
+
   PointSourcePannerDownmix::PointSourcePannerDownmix(
       std::shared_ptr<PointSourcePanner> psp, Eigen::MatrixXd downmix)
       : _psp(psp), _downmix(downmix){};

src/common/point_source_panner.hpp

@@ -116,6 +116,8 @@ namespace ear {
     virtual boost::optional<Eigen::VectorXd> handle(
         Eigen::Vector3d position) = 0;
     virtual int numberOfOutputChannels() const = 0;
+
+    virtual ~PointSourcePanner();
   };
 
   /** @brief Wrapper around multiple regions.