The "Next Article" button stays active even on the last page

[carlitocenteno]

The "Next Section/Article" button should be deactivated when on the very last page, and the same should go for the "Previous Section/Article" button on the first page/cover. Not only will this solve having dysfunctional GUI elements on a page but would also improve user experience.

It would be awesome if the buttons had an "active" class applied only when the next and previous pages were available...or an "inactive" class whenever there are no first and last page available. Then we can appropriately style them to our heart's content.