uialertcontroller is crashed (ipad)

func onClickRate(button: UIButton) {
	let sheet = UIAlertController.init(title: "提示", message: "选择播放速率", preferredStyle: .actionSheet)
	sheet.addAction(UIAlertAction.init(title: "1.0", style: .default, handler: { (action) in
		print("1.0")
	}))
	sheet.addAction(UIAlertAction.init(title: "1.5", style: .default, handler: { (action) in
		print("1.5")
	}))
	
	sheet.addAction(UIAlertAction.init(title: "2.0", style: .default, handler: { (action) in
		print("2.0")
	}))
	
	sheet.addAction(UIAlertAction.init(title: "cancel", style: .destructive, handler: nil))
	if let popoverPresentationController = sheet.popoverPresentationController {
		popoverPresentationController.sourceView = button
		popoverPresentationController.sourceRect = button.bounds
	}
	self.present(sheet, animated: true, completion: nil)
}