dispose method
Called by deactivate; should contain the object deactivation code.
If propose throws an Object, the default Actor implementation will
call dispose to clean up even a partially initialized object. The
deactivate method passes its argument to this method as a thrown
argument. A non-null thrown indicates that dispose was called during
the handling of a thrown object.
Implementation
@protected
@override
void dispose() {
_insert?.close();
_insert = null;
_update?.close();
_update = null;
_delete?.close();
_delete = null;
super.dispose();
}