message: Add check to ensure that an invalid index can't be used.
diff: @@ -107,7 +107,7 @@ void NotificationArea::onMouseDown(EventHandler::MouseButton button, int x, int
  }
  const auto index = notificationIndex({x, y});
  - if (index != NoSelection)
  + if (index != NoSelection && index < mNotificationList.size())
  {
  if (button == EventHandler::MouseButton::Left)
  {
  