https://stackoverflow.com/questions/19226965/how-to-hide-uinavigationbar-1px-bottom-line
nc.navigationBar.setBackgroundImage(UIImage(), for: .default)
nc.navigationBar.shadowImage = UIImage()
https://stackoverflow.com/questions/19226965/how-to-hide-uinavigationbar-1px-bottom-line
nc.navigationBar.setBackgroundImage(UIImage(), for: .default)
nc.navigationBar.shadowImage = UIImage()