backport bug fix

modules/photo/src/seamless_cloning_impl.cpp

@@ -512,10 +512,12 @@ void Cloning::illum_change(Mat &I, Mat &mask, Mat &wmask, Mat &cloned, float alp
     multiply(patchGradientX,pow(alpha,beta),multX);
     pow(mag,-1*beta, multx_temp);
     multiply(multX,multx_temp, patchGradientX);
+    patchNaNs(patchGradientX);
 
     multiply(patchGradientY,pow(alpha,beta),multY);
     pow(mag,-1*beta, multy_temp);
     multiply(multY,multy_temp,patchGradientY);
+    patchNaNs(patchGradientY);
 
     Mat zeroMask = (patchGradientX != 0);