ios导航栏的后退按钮在弹出框中没有响应

I'm maintaining an old code based on xib files. Everything worked fine, but recently, the back button of the navigation bar in a popover is no longer responding. I changed from using a UIPopoverController to presenting the navigation controller with UIModalPresentationPopover style but nothing changed. Here's what I'm doing:I'm maintaining an old code based on xib files.