Ipad彈出UIAlertControllerStyleActionSheet時發生崩潰

pad彈出UIAlertControllerStyleActionSheet時，在iphone上運行正常，但在ipad上崩潰，解決代碼以下：

UIAlertController *alertVc = [UIAlertController alertControllerWithTitle:@"請選擇圖片" message:@"" preferredStyle:UIAlertControllerStyleActionSheet];

 

    if (isiPad) {//判斷是否爲ipad

        UIPopoverPresentationController *popover = alertVc.popoverPresentationController;

        if (popover) {

            popover.sourceView = view;//視圖中的某個view

            popover.sourceRect = view.bounds;

            popover.permittedArrowDirections = UIPopoverArrowDirectionDown;//alertVC彈出的位置

        }

    }

    

    UIAlertAction *action1 = [UIAlertAction actionWithTitle:@"拍照" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {

        

    }];

    

    UIAlertAction *action2 = [UIAlertAction actionWithTitle:@"相冊" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {

    

    }];

    UIAlertAction *action3 = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleDestructive handler:^(UIAlertAction * _Nonnull action) {

        [alertVc dismissViewControllerAnimated:YES completion:nil];

    }];

    

    [alertVc addAction:action1];

    [alertVc addAction:action2];

    [alertVc addAction:action3];

    

    [self presentViewController:alertVc animated:YES completion:nil];