We can do this, because:
1. if `playQueue` is not null, we return early
2. if `playQueue` is null and we need to enqueue:
- the only “proper” case that could be triggered is
the `RESUME_PLAYBACK` case, which is never `true` for the queuing
intents, see the comment in `NavigationHelper.enqueueOnPlayer`
- the generic `else` case is degenerate, because it would crash on
`playQueue` being `null`.
This makes some sense, because there is no way to trigger the
enqueueing logic via the UI currently if there is no video playing
yet, in which case `playQueue` is not `null`.
So we need to transform this whole if desaster into a big switch.
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