System.Nullreferenceexception: Object Reference Not Set To An Instance Of An Object What Should I Do

public partial class WebForm2 : System.Web.UI.Page
    {
        [WebMethod]
        [ScriptMethod]
        
        public static Slide[] GetImages()
        {
            List<slide> slides = new List<slide>();
            string path = HttpContext.Current.Server.MapPath("~/Images/Images/");
            if (path.EndsWith("\\"))
            {
                path = path.Remove(path.Length - 1);
            }
            Uri pathUri = new Uri(path, UriKind.Absolute);
            string[] files = Directory.GetFiles(path);
            foreach (string file in files)
            {
                Uri filePathUri = new Uri(file, UriKind.Absolute);
                slides.Add(new Slide
                {
                    Name = Path.GetFileNameWithoutExtension(file),
                    Description = Path.GetFileNameWithoutExtension(file) + " Description.",
                    ImagePath = pathUri.MakeRelativeUri(filePathUri).ToString()
                });
            }
            return slides.ToArray();
        }
    }