Avoid a possible relcache leak in get_object_address_attribute.

There's no apparent way to trigger this, so I'm not going to worry
about back-patching it for now.  But it's still wrong.

Marti Raudsepp

src/backend/catalog/objectaddress.c

@@ -1024,6 +1024,7 @@ get_object_address_attribute(ObjectType objtype, List *objname,
 		address.classId = RelationRelationId;
 		address.objectId = InvalidOid;
 		address.objectSubId = InvalidAttrNumber;
+		relation_close(relation, lockmode);
 		return address;
 	}