Check to see whether the setting has an associated message before sending a notification.

And settlngs like flash are supposed to have notifications even though they are not part of the menu. So we don't want this sent from the settings menu code.  The settings library already emits an event when any settings value changes, I think. If we listen to that event somewhere, we can look at the notificationID for any setting that changes, and if it exists, display an appropriate notification.