skimage.transform.resize() crashes with a floating
point exception if the image has 1-pixel width or
height and the mode=“reflection”. Changing mode to
“constant” (the default) fixes the issue. And, 
it’s the correct mode to use anyway.

If the mask is a rectangle, its mini-mask pixels
become all 1s, and it has no zeros. Scipy imresize
fails on that and returns 0s instead. This update
fixes the problem.