Step 2 Stamps error during clap_fit

function [ph_out]=clap_filt(ph,alpha,beta,n_win,n_pad,low_pass)
CLAP_FILT Combined Low-pass Adaptive Phase filtering [ph_out]=CLAP_filt(ph,alpha,beta,n_win,n_pad,low_pass_fftshifted)
Andy Hooper, June 2006

if nargin<2
alpha=0.5;
end

if nargin<3
beta=0.1;
end

if nargin<4
n_win=32;
end

if nargin<5
n_pad=0;
end

if nargin<6 | isempty(low_pass)
low_pass=zeros(n_win+n_pad);
end

ph_out=zeros(size(ph));
[n_i,n_j]=size(ph);

n_inc=floor(n_win/4);
n_win_i=ceil(n_i/n_inc)-3;
n_win_j=ceil(n_j/n_inc)-3;

x=[0:n_win/2-1];
[X,Y]=meshgrid(x,x);
X=X+Y;
wind_func=[X,fliplr(X)];
wind_func=[wind_func;flipud(wind_func)];
wind_func=wind_func+1e-6; % so doesn’t go to zero in corners

ph(isnan(ph))=0;
B=gausswin(7)*gausswin(7)';
n_win_ex=n_win+n_pad;
ph_bit=zeros(n_win_ex);

for ix1=1:n_win_i
wf=wind_func;
i1=(ix1-1)*n_inc+1;
i2=i1+n_win-1;
if i2>n_i
i_shift=i2-n_i;
i2=n_i;
i1=n_i-n_win+1;
wf=[zeros(i_shift,n_win);wf(1:n_win-i_shift,:)];
end
for ix2=1:n_win_j
wf2=wf;
j1=(ix2-1)n_inc+1;
j2=j1+n_win-1;
if j2>n_j
j_shift=j2-n_j;
j2=n_j;
j1=n_j-n_win+1;
wf2=[zeros(n_win,j_shift),wf2(:,1:n_win-j_shift)];
end
ph_bit(1:n_win,1:n_win)=ph(i1:i2,j1:j2);
ph_fft=fft2(ph_bit);
H=abs(ph_fft);
H=ifftshift(filter2(B,fftshift(H))); smooth response meanH=median(H(:)); if meanH~=0 H=H/meanH; end H=H.^alpha; H=H-1; set all values under median to zero
H(H<0)=0; % set all values under median to zero
G=H
beta+low_pass;
ph_filt=ifft2(ph_fft.*G);
ph_filt=ph_filt(1:n_win,1:n_win).*wf2;
if isnan(ph_filt(1,1))
keyboard
end
ph_out(i1:i2,j1:j2)=ph_out(i1:i2,j1:j2)+ph_filt;
end
end

i get this oppened during the calculation patch phases it indicate to this statement
if isnan(ph_filt(1,1))
keyboard
end

is anyone know how to solve this problem ? Thank you for your advance