Bug 35405: Remove noise from MARC::Record in SearchAuthorities

Bug 35405: Remove noise from MARC::Record in SearchAuthorities

We are calling ->field with an undef parameter.
MARC::Record does not like that and says:
  Use of uninitialized value $tag in hash element at /usr/share/perl5/MARC/Record.pm line 202.
For now, a fix at our side.

Test plan:
Run SearchAuthorities without passing an authtypecode.
Without this patch, it results in a warning per hit.
With this patch, the noise should be gone.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>