Cascaded Folder make document writing fail

[GoogleCodeExporter]

Steps to reproduce the problem:
1. Create a new Kml.
2. Add a Folder to the Kml.
3. Add a Folder (with anything inside) to the previously added Folder.
4. Write Kml to file.

Seen result: Writing to file fails.
Expected result: Writing to file works (since it works in Google earth 
5.0) or an exception is raised when adding the Folder to another Folder 
(if it is not valid in KML).

KmlFramework version: 2009-03-20 (jar)
System: JDK 1.6 (XP SP3)

Original issue reported on code.google.com by [email protected] on 19 May 2009 at 1:47