[Zope] Sort in tree tag

[Lars Heber]

Hello,
I'd like to sort the folders in my tree tag by a property index.

The problem is that not every folder has this property.
So when I do
<tree ... sort=index>
I get an error, when a folder does not have that property index.
How can I avoid that error?
I'd like to do s. th. like
<tree ... (sort=index missing=0)>

Is that somehow possible?

Thanks.

--
Lars Heber, mailto:Lars.Heber@t-systems.de

T-Systems, debis Systemhaus GEI GmbH, Geschaeftsstelle Sachsen