page.next property in UI model should skip over reference to same page

If the next item in the navigation (assigned to page.next in the UI model) resolves to a deep link within the same page, the pager gets stuck on current page. In other words, click on "next page" just keeps linking back to a place within the current page. The logic that assigns the page.next property should continue looking until it finds a new page, thus skipping past entries that link to a different place in the same page.

page.previous and page.parent don't have this problem since the current page is already the first occurrence of that page in the navigation tree.