Fix for "Notice: Undefined variable: rota_order in /wp-content/plugins/church-admin/index.php on line 151/

When no rota jobs are present in the system, $rota_order never gets set as anything, hence the warning.

Setting $rota_order = null, fixes this notice, and (correctly?!) returns null when no rota jobs are returned.
Merge pull request #1 from JonB/hotfix/fix-undefined-variable-rota-order

Fix for "Notice: Undefined variable: rota_order in /wp-content/plugins/c...
Constants should be set by init action
Raise function version for Jon's fix