tracking: fix rounding error in trackerKCF

modules/tracking/src/trackerKCF.cpp

@@ -223,8 +223,8 @@ namespace cv{
 
     // create gaussian response
     y=Mat::zeros((int)roi.height,(int)roi.width,CV_64F);
-    for(unsigned i=0;i<roi.height;i++){
-      for(unsigned j=0;j<roi.width;j++){
+    for(unsigned i=0;i<(unsigned)roi.height;i++){
+      for(unsigned j=0;j<(unsigned)roi.width;j++){
         y.at<double>(i,j)=(i-roi.height/2+1)*(i-roi.height/2+1)+(j-roi.width/2+1)*(j-roi.width/2+1);
       }
     }