The startup catch cleared this.active unconditionally. In a stop()+restart
race during the slow login/pauses, the first attempt's catch would fire after
the second start() had already taken the lock, unlocking it mid-startup and
letting a third start() race in. Guard the active/state reset with
`this.controller === controller`, matching the field-null and playStream
.finally guards.
Verified live: stop during login then restart keeps the restart's lock
(active stays true), and it clears to false only once truly stopped; no crash.
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