Fix matching::maxDisparity value when calling StereoBinarySGBM::setNumDisparities after ctor

Note that it considers maxDisparity==numDisparities, and so minDisparity as being 0

modules/stereo/src/stereo_binary_sgbm.cpp

@@ -725,7 +725,8 @@ namespace cv
             void setMinDisparity(int minDisparity) CV_OVERRIDE {CV_Assert(minDisparity >= 0); params.minDisparity = minDisparity; }
 
             int getNumDisparities() const CV_OVERRIDE { return params.numDisparities; }
-            void setNumDisparities(int numDisparities) CV_OVERRIDE { CV_Assert(numDisparities > 0); params.numDisparities = numDisparities; }
+            void setNumDisparities(int numDisparities) CV_OVERRIDE { CV_Assert(numDisparities > 0); params.numDisparities = numDisparities;
+                                                                     Matching::setMaxDisparity(numDisparities /*- params.minDisparity*/);}
 
             int getBlockSize() const CV_OVERRIDE { return params.kernelSize; }
             void setBlockSize(int blockSize) CV_OVERRIDE {CV_Assert(blockSize % 2 != 0); params.kernelSize = blockSize; }