image_streamer: add virtual destructor such that subclass destructors can work

A classical C++ error, the delete was done on an ImageStreamer,
which has a non-virtual destructor, leading to the subclasses
destructor never being called, leading to memleaks.

Signed-off-by: Peter Soetens <peter@thesourceworks.com>

Author: Peter Soetens

include/web_video_server/image_streamer.h

@@ -16,6 +16,8 @@ class ImageStreamer
   ImageStreamer(const async_web_server_cpp::HttpRequest &request, async_web_server_cpp::HttpConnectionPtr connection,
                 image_transport::ImageTransport it);
 
+  virtual ~ImageStreamer();
+
   void start();
 
   bool isInactive();

src/image_streamer.cpp

@@ -14,6 +14,10 @@ ImageStreamer::ImageStreamer(const async_web_server_cpp::HttpRequest &request,
   invert_ = request.has_query_param("invert");
 }
 
+ImageStreamer::~ImageStreamer()
+{
+}
+
 void ImageStreamer::start()
 {
   image_sub_ = it_.subscribe(topic_, 1, &ImageStreamer::imageCallback, this);