Check that zone->view is not NULL before checking that zone->view->adb is not NULL.  It appears that zone maintenance can occur when the zone is shutting down and the view pointer is NULL.  We don't want to do zone maintenance in this case.
Check that zone->view is not NULL before checking that zone->view->adb is not
NULL.  It appears that zone maintenance can occur when the zone is shutting
down and the view pointer is NULL.  We don't want to do zone maintenance in
this case.

each/bind9-collab,pecharmin/bind9,pecharmin/bind9,each/bind9-collab,each/bind9-collab,each/bind9-collab,pecharmin/bind9,pecharmin/bind9,each/bind9-collab,pecharmin/bind9,pecharmin/bind9,each/bind9-collab