Bug 14555: Warns in opac-search.pl

Bug 14555: Warns in opac-search.pl

Avoid use of uninitialized value in split

== Test plan ==
1. Go to opac advanced search
2. Click "Search" without any search query
3. Log file will show "Use of uninitialized value in split at ..."
4. Apply this patch
5. Repeat step 1 and 2
6. Log file should no longer show "Use of uninitialized value in split at ..."

Sponsored-by: Regionbibliotek Halland / County library of Halland
Signed-off-by: Aleisha <aleishaamohia@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
At step 2 you have to check a criteria

Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>
(cherry picked from commit ab81a0feeebf1c01857755f53060dcc255960e9b)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>