Bug 15467: If authtypecode is not defined, do not explode

 Bug 15467: If authtypecode is not defined, do not explode

The test t/db_dependent/AuthoritiesMarc.t fails because one test expect
the BuildSummary subroutine to not crash if the authtypecode passed in
parameter does not exist in the DB.

Test plan:
prove t/db_dependent/AuthoritiesMarc.t
should return green.

Signed-off-by: Frédéric Demians <f.demians@tamil.fr>
  Test fails before patch, and doesn't anymore after.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>