Removed the resizeDuration if there is no resize nessesairy.

Possibly this is by design, if not, you might wish to apply this, (or similar patch).

Currently when no resize is needed, lightbox still waits for resizeDuration before showing the next image. This pull request fixes this.

This mainly enjoys me because it looks like my computer is working / the site is slow, while it's actually lightbox idling.