Bug 28365: (Bug 19873 follow-up) Make it possible to search on value 0

Bug 28365: (Bug 19873 follow-up) Make it possible to search on value 0

Bug 19873 fixed search with value 0.
It works in first page but not in other pages.

This patch fixes query_cgi var.

Test plan:
  - create a st-numeric index in zebra conf related to
    a numeric field
    i.e:
    yourindex 1=yourindex 4=109
  - fill a field with 0 in several biblio records,
  - reindex your biblios,
  - search yourindex=0 and go to second page of results,
  - should not work,
  - apply this patch,
  - test again,
  - should work

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>