People who are flicking through navigation like that are expecting to click in the same place all the time. The simple fact is that most users don't look when they are clicking "next" on each page / screen.
If you start removing items from your navigation because they don't apply for that particular page, the other navigation links will move relative to where they were before. This could cause the user to click on the wrong thing, or be suddenly not clicking on anything. This can be a jarring experience.
I would say that keeping the positions of all links the same and disabling / greying out the ones that aren't relevent will give the best user experience.