Bug 36438: Check object for calling metadata

Bug 36438: Check object for calling metadata

Resolve: Can't call method "metadata" on an undefined value at catalogue/MARCdetail.pl line 93

The proceeding lines check for $record and respond appropriately.

Test plan:
Call catalogue/MARCdetail.pl with an unexisting biblionumber.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Emily Lamancusa <emily.lamancusa@montgomerycountymd.gov>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>