fix: Update isPlaying on main thread

- 뷰와 관련된 published 프로퍼티의 값 변경을 메인 스레드에서 하도록 수정

MinGenie/MinGenie/Playback/MusicPlayerModel.swift

@@ -248,7 +248,9 @@ final class MusicPlayerModel: ObservableObject {
     }
 
     private func handlePlaybackStateDidChange() {
-        isPlaying = (musicPlayer.state.playbackStatus == .playing)
+        DispatchQueue.main.async {
+            self.isPlaying = (self.musicPlayer.state.playbackStatus == .playing)
+        }
     }
 
 }