[RESOLVED] NullReferenceException when adding to list

[Cyb3rH4Xter]

I thought that I knew how to handle those NullReferenceExceptions...but I simply don't know what to do with this one

Part of my Code:

        public class Chapter
        {
            public string Name;
            public TimeSpan Time;
        }

        public class ChapterSet
        {
            public List<Chapter> Chapters;
        }

        public ArrayList GrabChapters(string searchString)
        {
           
            ...(Unimportant code)...

            foreach (XmlNode node in NodeList)
            {
                ChapterSet chapterSet = new ChapterSet();

                XmlNodeList chapters = node.ChildNodes;
                foreach (XmlNode chapter in chapters)
                {
                    Chapter pChapter = new Chapter();
                    pChapter.Name = chapter.Attributes["name"].Value;
                    pChapter.Time = TimeSpan.Parse(chapter.Attributes["time"].Value);

                    chapterSet.Chapters.Add(pChapter);
                }

                Results.Add(chapterSet);
            }

            return Results;
        }

Anyone that can give a good explanation why this happens? (On the red line)