[Zope] Problem with Topic Index

[Vladimir Petrovic]

I have a trange problem with topic index (on Zope 2.6.1 running on Linux). I 
created a filtered set with the expression (o.title == 'aa'). I catalogued 
only one document (this document has title 'aa') and filtered set reports it 
has one document.

Then I went to the Catalog of the ZCatalog, and I removed the catalogued 
object. All indexes removed the object except this filtered set which still 
contains one object (ZCatalog itself contains zero objects). And then 
querying topic index with this filtered set produces KeyError in ZCatalog.

It seems like topic index is ignoring unindex operation.  Is there anything 
special that needs to be done with topic indexes ?

Vladimir