Error with Google IMA SDK for Flash

Hi I am receiving the error below after an ad of video type is found and while the adsManager plays the ad.

My code is:

private function onAdsLoadedListener(e:AdsLoadedEvent):void {
    // ...
    _adsManager = e.adsManager;
    _adsManager.load(_videoOnStage);
    _adsManager.play(_videoOnStage);
}

The error I get from Google IMA is:

Error: ErrorCode: 0AdError: Error #1034: Type Coercion failed: cannot convert "null" to XMLList.

Error: A开发者_StackOverflow社区d adPlayError error: Error #1034: Type Coercion failed: cannot convert "null" to XMLList. errorCode: 0