message: only set the player as stopped when it's still scheduled as playing
  addresses
diff: @@ -155,7 +155,8 @@ export class Player extends Source<PlayerOptions> {
  // delete the source from the active sources
  this._activeSources.delete(source);
  - if (this._activeSources.size === 0 && !this._synced) {
  + if (this._activeSources.size === 0 && !this._synced &&
  + this._state.getValueAtTime(this.now()) === "started") {
  this._state.setStateAtTime("stopped", this.now());
  }
  }
  