SH-4242 FIX interesting: Mac viewer crashes on exit

made notifications subsystem touch instancetracker<notificationchannel>
in constructor so that teardown order is preserved

indra/llui/llnotifications.cpp

@@ -1207,6 +1207,9 @@ LLNotifications::LLNotifications()
 	mIgnoreAllNotifications(false)
 {
 	LLUICtrl::CommitCallbackRegistry::currentRegistrar().add("Notification.Show", boost::bind(&LLNotifications::addFromCallback, this, _2));
+
+	// touch the instance tracker for notification channels, so that it will still be around in our destructor
+	LLInstanceTracker<LLNotificationChannel, std::string>::instanceCount();
 }