how to solve "Attempt to grow array along ambiguous dimension." error?

I recived an error when i run my code in matlab as Attempt to grow array along ambiguous dimension.How can i solve it.here i attached my code.Those two images(img1,img2) are 8 depth image.

img1 = imread('PlotEdited.bmp');
img2 = imread('002skullOnly.bmp');

figure(1);
imshowpair(img1,img2,'montage'); % Show two images

[optimizer,metric]=imregconfig('multimodal');

registered=imregister(img1,img2,'similarity',optimizer,metric); % Register images

[centres,radii] = imfindcircles(registered, [20 25],...
    'objectPolarity','dark',...
    'sensitivity',0.94);
figure(2);imshow(registered);
viscircles(centres,radii);

BW=imbinarize(registered(:,:,1));
img=registered;
img(repmat(~registered,1,1,3))=255; %%ERROR Attempt to grow array along ambiguous dimension
figure(3);imshow(img);

figure(4);
imshowpair(registered,img2);title('Registration','fontSize',12)
saveas(4,'002Registered.bmp','bmp');