Bug 9832: avert software error with QP enabled and misconfigured

Bug 9832: avert software error with QP enabled and misconfigured

QueryParser requires a configuration file. If koha-conf.xml does not
point to that configuration file, you will get a software error when
you try to search with QueryParser enabled. Until this patch.

To test:
1) Comment out the <queryparser_config> line in your koha-conf.xml
2) Turn on UseQueryParser
3) Do a search, watch it explode
4) Apply patch
5) Do search again, watch it work
6) Sign off on patch

Signed-off-by: Mirko Tietgen <mirko@abunchofthings.net>
Works as expected, nothing explodes anymore

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>