Bug 12481: Staff client detail-view "next" link is greyed out when the last search...

Bug 12481: Staff client detail-view "next" link is greyed out when the last search result of any results page is clicked or navigated into

When doing a staff client catalog search with more than 1 page of results
and clicking the last result on any search result page, the top-left navigation
button for "next" is greyed out.

Tested on newest Firefox & Chromium. Attempts to restore originally planned checks for navigation
with the exception of not using results.length due to buggy behaviour where the results get concatenated
upon page reload & "return to results" navigation - a separate issue?

To test:
1) Do an intranet catalog search that has more than 1 page of results.
2) Click on the last result on a page that is not the last one & confirm that the navigation button "next" is greyed out.
4) Apply patch.
5) Do an intranet search with more than 1 but less results than fit on a single page.
6) Click on the last result on the page and confirm that the "Next" navigation button is greyed out.
6) Do an intranet search with more than 1 page of results.
7) Click on the last result of a page that's not the final page of the results & confirm that "Next" is not grey out.
8) Navigate to the last page of the results and click on the final result & confirm that "Next" is greyd out.

http://bugs.koha-community.org/show_bug.cgi?id=12481

This patch prevents the "Next" button on detail view to be grayed out at the end of e result page.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>