Whether a VideoNotification is visually present (including during its fade-out animation). Lives as a free function — not a method on VideoNotification — precisely so it can guard a possibly-invalid reference: callers pass m.segmentNotification / m.nextEpisodeNotification, which can be cleared during player teardown (VideoPlayerView.onDestroy) while an observer such as onPositionChanged still fires. A method (node.callFunc(...)) could not guard its own non-existence and would crash the same way the caller does.

A notification that doesn't exist is, by definition, not visible → false.