awesome_nested_set help needed

Hello,

I've been using the brilliant awesome_nested_set gem to manage pages
and their parents on my app, however I've run into what appears to be
a simple challenge...

I use the helper nested_set_options to make life easier - however I
can't see if there is an easy way I can get it to return a NULL option
at the top of the select list? This would allow me to create pages
that are roots.

Any advice would be greatly appreciated.

Kind regards,
Ian