FIX: prevents rendering empty timeline-controls (PR #9304)

The streamlength/height code when true would return just after we had inserted the timeline-controls, resulting, on topic-progress event to display an empty timeline-controls when clicked.

I think this code in unecessary and we should only rely on the code in hideProgress which will currenly hide the progress is the stream has only one post displayed on desktop (always shown on mobile).


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Sounds reasonable to me!