Bug 20443: Do not explode if attribute does not have a valid av

Bug 20443: Do not explode if attribute does not have a valid av

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>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>