Zero-valued spacing is not supported and may result in undefined behavior.

Thanks for your reply, @zivy

I know the image is all zeros, it is a top left subtile of a larger image for registration, it is all zeros as it is out of the FoV of the moving image:

I would expect that in this case it would just return a zero of inf or something like that? no?
I assume if I just add some very small noise to these ares it will be ok?
Any thoughts?

Thanks