Behave if child atom is empty (#170)

Credit: https://github.com/ta264
Lidarr#5

Author: decriptor

src/TaglibSharp/Mpeg4/Box.cs

@@ -456,6 +456,9 @@ protected IEnumerable<Box> LoadChildren (TagLib.File file)
 			header.Box = this;
 			while (position < end) {
 				Box child = BoxFactory.CreateBox (file, position, header, Handler, children.Count);
+				if (child.Size == 0)
+					break;
+
 				children.Add (child);
 				position += child.Size;
 			}

src/TaglibSharp/Mpeg4/Boxes/UnknownBox.cs

@@ -64,13 +64,12 @@ public class UnknownBox : Box
 		/// <exception cref="ArgumentNullException">
 		///    <paramref name="file" /> is <see langword="null" />.
 		/// </exception>
-		public UnknownBox (BoxHeader header, TagLib.File file, IsoHandlerBox handler)
-			: base (header, handler)
+		public UnknownBox (BoxHeader header, TagLib.File file, IsoHandlerBox handler) : base (header, handler)
 		{
 			if (file == null)
 				throw new ArgumentNullException (nameof (file));
 
-			data = LoadData (file);
+			data = file.ReadBlock (DataSize > 0 ? DataSize : 0);
 		}
 
 		#endregion