If a image exist, it's a link to the image page. If a image doesn't exist, the
image link points to the upload page: "be bold and upload it!" Ok. But if you
don't allow uploading, it is unsense. So if a wiki have uploading disabled,
non-existant image links should point to the image page ('we have no such
image') instead of the upload page ('you can't upload, it's disabled') as the
user didn't ask for uploading an image, only followed an image link (which only
wikiholics understand as a link-to-upload).