[BUGFIX] Next/last button not linked on last page

The button icon viewhelper now supports an empty uri parameter. The
link on the next / last button of the backend paginate widget in case
you are on the very last page can be removed.

Change-Id: I238c77efa8a9d4ff4a1864f6df876a695dc690e5
Resolves: #51395
Releases: 6.2
Reviewed-on: https://review.typo3.org/23363
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters