loadImageFromDisk - function modyfication swift

im using the below code to load a downloaded image from disk, when the file exists I can load it as image. If it doesn't image returns as nil.

How could I modify the code to replace return nil with loading a placeholder image from my asset folder called default.png. So instead of returning nil, there is always an image return, either downloaded one that's trying to load or if it doesn't exist, my own asset image.

func loadImageFromDiskWith(fileName: String) -> UIImage? {
  let documentDirectory = FileManager.SearchPathDirectory.documentDirectory

    let userDomainMask = FileManager.SearchPathDomainMask.userDomainMask
    let paths = NSSearchPathForDirectoriesInDomains(documentDirectory, userDomainMask, true)

    if let dirPath = paths.first {
        let imageUrl = URL(fileURLWithPath: dirPath).appendingPathComponent(fileName)
        let image = UIImage(contentsOfFile: imageUrl.path)
        return image
    }
    return nil
}

You can do as below -

func loadImageFromDiskWith(fileName: String) -> UIImage {
  let documentDirectory = FileManager.SearchPathDirectory.documentDirectory

    let userDomainMask = FileManager.SearchPathDomainMask.userDomainMask
    let paths = NSSearchPathForDirectoriesInDomains(documentDirectory, userDomainMask, true)
    var image = UIImage(named: "default") // Make sure there must be "default.png" in your main bundle.
    if let dirPath = paths.first {
        let imageUrl = URL(fileURLWithPath: dirPath).appendingPathComponent(fileName)
        if FileManager.default.fileExists(atPath: imageUrl.path) { //Check here for file existence. It won't crash.
              image = UIImage(contentsOfFile: imageUrl.path)
         }
    }

    return image
}