Bug 21036: Remove odd number of elements warnings from AuthoritiesMarc.pm

Bug 21036: Remove odd number of elements warnings from AuthoritiesMarc.pm

Like this one (16.11 line number):
Odd number of elements in anonymous hash at C4/AuthoritiesMarc.pm line 1070.

We need to add a scalar to some MARC::Field::subfield calls. In list context
an empty list returned affects the hash built around it.

Test plan:
Could reproduce this warning easily from OPAC authority search.
opac-authorities-home.pl calling BuildSummary.

Signed-off-by: Bouzid Fergani <bouzid.fergani@inlibro.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>