Bug 8914: Blank search that returns invalid authorities fails under Plack

Bug 8914: Blank search that returns invalid authorities fails under Plack

When doing a search with no terms for the default authority type under
Plack, you will get a segfault if it returns any records that do not
have any authority type. As far as I can tell, this cannot be reproduced
under CGI/Apache.

To test:
Confirm that you don't get an error if you click the Submit button in
the authorities sections in the staff client and OPAC without entering
a term or changing the authority type.

You may or may not be able to reproduce the problem prior to applying
the patch, but that is the only situation in which I managed to trigger
it.

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>