Unfortunately we could not reproduce this exception. What version are you using?
I have attached a small sample project. You can modify it to reproduce the error you are getting, send it back to us and tell us what are the exact steps we need to do in order to get the exception.
Alternatively, if it would be easier for you, you can create your own sample dummy project and send it to us. Again, let us know what we should do to make it crash.
We are looking forward to hearing from you.
the Telerik team