Fix the crash in iOS6 when you start a not supported video

// Fix the crash in iOS6 when you start a not supported video stream
// note: do not use initWithUrl, instead use setContentURL
MPMoviePlayerViewController viewController = [[MPMoviePlayerViewController alloc] init];
viewController.moviePlayer.movieSourceType = MPMovieSourceTypeStreaming;
viewController.moviePlayer.controlStyle = MPMovieControlStyleFullscreen;
[viewController.moviePlayer setContentURL:url];