Bug in full/image.tpl, the next / prev links are buggy when the sorting is set to class_identifier, depth, class_name, section or priority on parent gallery.

On some of those direction on navigation changes and when you navigate to the first element you will still get a link to 'next' witch is the same element that you are viewing.

Steps to reproduce

1.Create a gallery and sett sorting to name
2.add 2 pictures
3.Navigate to second image in gallery in public site, every thing should be fine.
4.Change the sorting to one of the ones mentioned above
(remember to cleare view cache if it's on)
5.Refresh the public site on the second image, on some of the sortings the direction changes and if you navigate to picture1 you will on some of the sortings not be able to navigate back

Repeat step 4 and 5 for all mentioned sorting methodes.