T5 : how to handle a zone refresh when the user session has expired ?

[Stephane Decleire]

I get the following error when trying to refresh a Zone in my 
application while the user session has expired :

org.apache.tapestry5.runtime.ComponentEventException
Forms require that the request method be POST and that the t:formdata 
query parameter have values.

Any idea on how and where i can handle this exception to show the user a 
better result than a blank zone ?

Thanks in advance.

Stephane