Fix missing isDestroyed check in StreamingService
Fix missing isDestroyed check in StreamingService

streamlink/streamlink-twitch-gui,streamlink/streamlink-twitch-gui,bastimeyer/livestreamer-twitch-gui,chhe/livestreamer-twitch-gui,bastimeyer/livestreamer-twitch-gui,chhe/livestreamer-twitch-gui,bastimeyer/livestreamer-twitch-gui,streamlink/streamlink-twitch-gui,chhe/livestreamer-twitch-gui