iPad展示UIAlertController崩溃解决

The modalPresentationStyle of a UIAlertController with this style is UIModalPresentationPopover. You must provide location information for this popover through the alert controller's popoverPresentationController

iPhone和iPad使用UIAlertController展示ActionSheep时，展示是不一样的。
所以在iPhone上正常显示的AlertController，在iPad上显示要添加几行代码

        let popover = alertVc.popoverPresentationController
        if (popover != nil) {
            popover?.sourceView = sender
            popover?.sourceRect = sender.bounds
            popover?.permittedArrowDirections  = .any
        }