Bug 12261: Staff client next/previous links lead to unknown record

Bug 12261: Staff client next/previous links lead to unknown record

When using Staff client next/previous links after a search :
If the current record is the last of the results, clicking on "next"
will lead to the page of an unknown record with message :

The record you requested does not exist (NaN).

To test:
1) Do an intranet catalog search that has more than 1 results.
2) Click on the last search result and then click the "Next"-button from
   the top-left navigation.
3) Confirm that you get thrown to a page with the message: "The record
   you requested does not exist (NaN).".
4) Apply patch.
5) Repeat steps 1 - 2.
6) Confirm that the navigation button for "Next" is greyed out.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
This patch fixes the problem with last result in both single pages of
search results and multiple pages of search results.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>