calib3d: fix fisheye for test fisheyeTest.stereoCalibrateFixIntrinsic

modules/calib3d/src/fisheye.cpp

@@ -1040,7 +1040,9 @@ double cv::fisheye::stereoCalibrate(InputArrayOfArrays objectPoints, InputArrayO
         int b = cv::countNonZero(intrinsicRight.isEstimate);
         cv::Mat deltas;
         solve(J.t() * J, J.t()*e, deltas);
+        if (a > 0)
             intrinsicLeft = intrinsicLeft + deltas.rowRange(0, a);
+        if (b > 0)
             intrinsicRight = intrinsicRight + deltas.rowRange(a, a + b);
         omcur = omcur + cv::Vec3d(deltas.rowRange(a + b, a + b + 3));
         Tcur = Tcur + cv::Vec3d(deltas.rowRange(a + b + 3, a + b + 6));