manual detection and fix:

mysql> select * from _Member where _orderPriority is null;
+---------------+----------------------------------+---------------------+---------------------+------------------+------------------+--------------------------+-------------------------+----------------------------------+----------------------------------+----------------------------------+-----------+------------+------------------------+----------------+-----------------------+
| DISCRIMINATOR | id                               | _created            | _modified           | version_opt_lock | Member_committee | Member_conferenceEdition | Member_conferenceSeries | Member_event                     | Member_person                    | Member_role                      | _showRole | _listFirst | _notificationProcessed | _orderPriority | Member_programSession |
+---------------+----------------------------------+---------------------+---------------------+------------------+------------------+--------------------------+-------------------------+----------------------------------+----------------------------------+----------------------------------+-----------+------------+------------------------+----------------+-----------------------+
| Member        | 2940434f16324b089a5bff5968067cad | 2015-09-14 05:01:13 | 2015-09-14 05:17:21 |                4 | NULL             | NULL                     | NULL                    | d927e3c6893b4344859126e934e4ab2d | 985a8808b6e34963b4873917adbad02c | 358ae43028f14ceb952c333e41e45da9 |           |            |                       |           NULL | NULL                  |
+---------------+----------------------------------+---------------------+---------------------+------------------+------------------+--------------------------+-------------------------+----------------------------------+----------------------------------+----------------------------------+-----------+------------+------------------------+----------------+-----------------------+
1 row in set (0.01 sec)



mysql> update _Member set _orderPriority = 0 where _orderPriority is null limit 1;
Query OK, 1 row affected (0.08 sec)

Submitted by Danny Groenewegen on 14 September 2015 at 09:51

This is a recurring issue. WebDSL should generate code that handles NPE in sorting.

https://github.com/webdsl/webdsl/commit/c98ad4fd108f6c28d59f0940d09d0414f438f60a