Receiving error Output argument "V" (and maybe others) not assigned during call to "C:\Users\​jhilam\Dow​nloads\ima​gefilterde​mo\create_​variance.m​>create_va​riance".

I want to calculate variance of an image. my code look like

function V=create_variance(I)
  [M N]=size(I);
 % I(i,j)=zeros(12);
 X=0;
 tot_intensity=0;
  for i=1:M
      for j=1:N
          tot_intensity=tot_intensity+I(i,j);
      end
  end
  mean_intensity=tot_intensity/(M*N)
  for i=1:M
      for j=1:N
          X=X+(I(i,j)-mean_intensity);
          X=X*X*X;
      end
  end
  A=X/M*N;
end
while I executed main function I received above error.
How can I overcome this error