PCQI code doesn't showing any output neither any error

I need to take output from a "PCQI: A Patch-Structure Representation Method for Quality Assessment of Contrast Changed Images" code. But whenever i run this, it doesnt show anything at all. Not even an error. How can i solve this?

Demo.m

clc;
clear;

im1=imread('ref.png');
im2=imread('contrast_changed.png');
im1=double(rgb2gray(im1));
im2=double(rgb2gray(im2));
[mpcqi, pcqi_map] = PCQI(im1, im2);

PCQI.m (default value for window = fspecial('gaussian', 11, 1.5); L = 256)

function [mpcqi, pcqi_map]= PCQI(img1, img2, window, L)
if (nargin < 2 || nargin > 4)
   mpcqi = -Inf;
   pcqi_map = -Inf;
   return;
end

if (size(img1) ~= size(img2))
   mpcqi = -Inf;
   pcqi_map = -Inf;
   return;
end

[M N] = size(img1);

if (nargin == 2)
   if ((M < 11) || (N < 11))
	   mpcqi    = -Inf;
	   pcqi_map = -Inf;
      return
   end
   window = fspecial('gaussian', 11, 1.5);	
   L = 256;                                 
end

if (nargin == 3)
   [H W] = size(window);
   if ((H*W) < 4 || (H > M) || (W > N))
	   mpcqi = -Inf;
	   pcqi_map = -Inf;
      return
   end
   L = 255;
end

if (nargin == 4)
   [H W] = size(window);
   if ((H*W) < 4 || (H > M) || (W > N))
	   mpcqi = -Inf;
	   pcqi_map = -Inf;
      return
   end
end

window = window/sum(sum(window));
   
mu1    = filter2(window, img1, 'valid');
mu2    = filter2(window, img2, 'valid');
mu1_sq = mu1.*mu1;
mu2_sq = mu2.*mu2;
mu1_mu2 = mu1.*mu2;
sigma1_sq = filter2(window, img1.*img1, 'valid') - mu1_sq;
sigma2_sq = filter2(window, img2.*img2, 'valid') - mu2_sq;
sigma12   = filter2(window, img1.*img2, 'valid') - mu1_mu2;

      
sigma1_sq = max(0, sigma1_sq);
sigma2_sq = max(0, sigma2_sq);
 
C=3;

pcqi_map  =   (4/pi) *atan((sigma12 + C )./(sigma1_sq + C ));
pcqi_map  =   pcqi_map .*((sigma12 + C)    ./(sqrt(sigma1_sq).*sqrt(sigma2_sq) + C));
pcqi_map  =   pcqi_map .*exp(-abs(mu1-mu2)/L);

mpcqi     = mean2(pcqi_map);

return