[Zope] len() of unsized object

[Frank Tegtmeyer]

I have the following DTML code:

<dtml-in  ZSQL_method>
   <dtml-if email2><dtml-var email2></dtml-if>
</dtml-in>

ZSQL_method is a select * where key=xxx and gives exactly one row.

Zope gives the following error:

Error Type: TypeError
Error Value: len() of unsized object

It is only produced if email2 is not NULL. If I include email2 without
the test it works - but then I include also NULL values.
The error is also generated if I use <dtml-if "_['sequence-item'].email2">

I looked at this error type and found only references to some odd
sendmail tag behaviour. Can anybody give me a hint, where to look and
what to look for?

Software:
MySQL 3.22.32
Zope 2.3.0
MySQLDA 2.0.4
Python 1.52


Regards, Frank