如何解决UIAlertController (ActionSheet)在xamarin.ios原生app的iPad上崩溃？

UIViewController currentViewController = UIApplication.SharedApplication.KeyWindow.RootViewController;
while (currentViewController.PresentedViewController != null)
{
    currentViewController = currentViewController.PresentedViewController;
}

if (UIDevice.CurrentDevice.UserInterfaceIdiom == UIUserInterfaceIdiom.Pad)
{
    // 在iPad上进行处理
}

UIAlertController alertController = UIAlertController.Create("标题", "消息", UIAlertControllerStyle.ActionSheet);

// 添加Action按钮

// 创建UIPopoverPresentationController
UIPopoverPresentationController popoverPresentationController = alertController.PopoverPresentationController;
if (popoverPresentationController != null)
{
    popoverPresentationController.SourceView = currentViewController.View;
    popoverPresentationController.SourceRect = new CGRect(currentViewController.View.Bounds.GetMidX(), currentViewController.View.Bounds.GetMidY(), 0, 0);
    popoverPresentationController.PermittedArrowDirections = UIPopoverArrowDirection.Any;
}

currentViewController.PresentViewController(alertController, true, null);