Orbit fix / Run images_loaded callback if images.length == 0

This caused the orbit slider to not load/init. If orbit is used as content slider and not as images slider than the callback image_loaded in L287 (foundation.orbit.js) is never fired.

So the callback needs also to be fired if the image array is empty.

Related issues:
http://foundation.zurb.com/forum/posts/2144-orbit-not-visible-on-load-when-interchange-used-for-images