Bug 35833: Silence few warnings from searching

Bug 35833: Silence few warnings from searching

Resolve:
[2024/01/18 11:31:24] [WARN] Use of uninitialized value $hits in numeric eq (==) at /usr/share/koha/opac/opac-search.pl line 612.
[2024/01/18 11:31:24] [WARN] Use of uninitialized value $times in subtraction (-) at /usr/share/koha/C4/Search.pm line 1715.

Test plan:
Look for a few search expressions without results.
Check log without and with patch.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>