Prevent a MARC::File::XML error from killing authority_control_fields.pl batch

Prevent a MARC::File::XML error from killing authority_control_fields.pl batch

Continuing to make this script bullet-proof, MARC::File::XML cares deeply
about things like whether datafields have indicators and throws exceptions
that, if not caught, kill a processing script - like this one.

Borrowing the approach from marc_export, wrap the new_from_xml() call in
a try / otherwise block and roll on.

Signed-off-by: Dan Scott <dscott@laurentian.ca>
git-svn-id: svn://svn.open-ils.org/ILS/trunk@20332 dcc99617-32d9-48b4-a31d-7c20da2025e4