Template process failed: undef error - Can't call method "lib" on an undefined value at /kohadevbox/koha/Koha/Patron/Attribute.pm line 109.                                                                         at /kohadevbox/koha/C4/Templates.pm line 122

We should not crash as it if the attribute is linked to an invalid
authorised value (for instance the AV has been deleted)

We must provide a check in the search_for_data_inconsistencies.pl script

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>