swift - SLComposeViewController 错误 => LaunchServices：调用了 invalidationHandler

Question

我正在我的 SpriteKit 游戏（iOS 8 + Swift）中集成社交分享。一切正常，但我收到以下错误：“LaunchServices：invalidationHandler called”。知道如何解决错误吗？这是我的代码：

func shareWithFacebook() {

    if SLComposeViewController.isAvailableForServiceType(SLServiceTypeFacebook) {
        let facebookSheet = SLComposeViewController(forServiceType: SLServiceTypeFacebook)
        facebookSheet.setInitialText("Test FB post with score of \(score)")
        self.presentViewController(facebookSheet, animated: true, completion: nil)
    } else {
        println("facebook not available")
    }

}

我也尝试在呈现 ViewController 之前添加一个 sourceView，但仍然出现错误...

facebookSheet.popoverPresentationController?.sourceView = self.view