Silva Rc4 upgrade problem

Hi,

I have site operational under Silva 0.9.2
In order to move towards 1.0(Rc4) I upgraded to Silva 0.9.3.6. This did 
not give errors. Although I have not looked whether the site was still 
functional.
Next I want to upgrade to Silva 1.0RC4.

I did a Refresh all and next 'upgrade content'.
I immediately get the following error:

Time 2004/07/07 13:53:29.321 GMT+2
User Name (User Id) webmaster (webmaster)
Request URL 
http://bocpc1.chem.uu.nl:8080/silva/service_extensions/upgrade_all
Exception Type TypeError
Exception Value coercing to Unicode: need string or buffer, NoneType found

Traceback (innermost last):
  Module ZPublisher.Publish, line 101, in publish
  Module ZPublisher.mapply, line 88, in mapply
  Module ZPublisher.Publish, line 39, in call_object
  Module Products.Silva.ExtensionService, line 92, in upgrade_all
  Module Products.Silva.Root, line 202, in upgrade_silva
  Module Products.Silva.upgrade, line 159, in upgrade
  Module Products.Silva.upgrade, line 114, in upgradeTree
  Module Products.Silva.upgrade, line 92, in upgradeObject
  Module Products.Silva.upgrade_100, line 35, in upgrade
  Module Products.Silva.Image, line 475, in _createDerivedImages
  Module Products.Silva.Image, line 479, in _createWebPresentation
  Module Products.Silva.Image, line 228, in getCanonicalWebScale
  Module Products.Silva.Image, line 309, in getDimensions
  Module Products.Silva.Image, line 621, in _get_dimensions_from_image_data
  Module Products.Silva.Image, line 467, in _getPILImage
  Module Products.Silva.Image, line 638, in _get_image_data
TypeError: coercing to Unicode: need string or buffer, NoneType found

???????
NOTE:
I also create a new, bare Silva Root. I could perfectly use PIL to 
include and scale images within the new Silva.

Is there (already) a method to do partial upgrades? This may help in 
locating the problem....

Any help is welcome.
Bas

-- 
Dr. Bas R. Leeflang
Bijvoet Center for Biomolecular Research Tel : +31.30.253.3498
Utrecht University                       Fax : +31.30.254.0980
Padualaan 8, NL-3584 CH  Utrecht         Email: [email protected]
The Netherlands                          http://www.bijvoet-center.nl