[Zope] specifying empty action for zmi tab

[zope at netchan.cotse.net]

I have the following class:

class VirtualFile(Tabs, Implicit):
    "Wrapper around a file on the filesystem."
    [snip]
 
    manage_options = (({'label' : 'Info', 'action' : 'manage_main'},
                       {'label' : 'View/Download', 'action' : ''},
                       ))
    [snip]


Let's suppose, I'm in zmi and access the management screen of an
instance of this class via the following url:

http://127.0.0.1:8002/Instances/tempo/ExternalFolder/EFExceptions.py/man
age_main

The link for the first management tab is just fine (href="manage_main"),
but the second one (View/Download) is wrong, it's:
href="http://127.0.0.1:8002/Instances/tempo/ExternalFolder".
If I change the action field of 'View/Download' to 'index_html', the
generated url will be okay again: href="index_html".
What should I write in the action field to provide
"http://127.0.0.1:8002/Instances/tempo/ExternalFolder/EFExceptions.py"
as the url?

Regards,
Sandor