prevent NoMethodError: undefined method `serialized?' for nil in tls …

…option migration

the 'ldap_tls_options' setting does no longer exist and has therefore no format de
fined in the current code

we also fixed the value/deserialize to handle this more gracefully, but for good measure we also just pick the value directly here because that is more robust

db/migrate/20221115082403_add_ldap_tls_options.rb

@@ -42,7 +42,7 @@ def change
         # Current LDAP library default is to not verify the certificate
         MigratingAuthSource.reset_column_information
 
-        ldap_settings = Setting.find_by(name: "ldap_tls_options")&.value
+        ldap_settings = Setting.where(name: "ldap_tls_options").pick :value
         migrate_ldap_settings(ldap_settings)
       end
     end