Tried to pop to a view controller that doesn't exist.

试图pop一个已经不存在的视图控制器

解决办法:

for (UIViewController *controller in self.navigationController.viewControllers) {
      if ([controller isKindOfClass:[YWZViewController class]]) {
               YWZViewController *chooseSecurityVC =(YWZViewController *)controller;
               chooseSecurityVC.obj_id = _releaseModel.id;
               [self.navigationController popToViewController:chooseSecurityVC animated:YES];
        }
 }