[Simple-support] UnionList with empty list

[Christopher K. <ki...@na...>]

I'm trying to use UnionList to persist a list of mixed-class elements, 
where the list may also be empty. I can replicate the tutorial example 
just fine when there are items in the list. But if I try with an empty 
list, I get:
<task name="setup">
<delete/>
</task>

Is it possible to set the list as not required? I would like to see 
output as:
<task name="setup">
</task>

Thanks,
Chris