fixed a few problems detected by Xcode 4.2.1

modules/contrib/src/chamfermatching.cpp

@@ -72,6 +72,7 @@ private:
     class ImageIterator
     {
     public:
+        virtual ~ImageIterator() {}
         virtual bool hasNext() const = 0;
         virtual location_scale_t next() = 0;
     };

modules/contrib/src/retinafilter.hpp

@@ -304,7 +304,11 @@ public:
 	/**
 	* @return the input image sampled by the photoreceptors spatial sampling
 	*/
-	inline const std::valarray<float> &getPhotoreceptorsSampledFrame() const {if (_photoreceptorsLogSampling)return _photoreceptorsLogSampling->getSampledFrame();};
+	inline const std::valarray<float> &getPhotoreceptorsSampledFrame() const
+    {
+        CV_Assert(_photoreceptorsLogSampling);
+        return _photoreceptorsLogSampling->getSampledFrame();
+    };
 
 	/**
 	* @return photoreceptors output, locally adapted luminance only, no high frequency spatio-temporal noise reduction at the next retina processing stages, use getPhotoreceptors method to get complete photoreceptors output