Update from Perch 2.7.2 categories problem

I'm testing update of a site from Perch 2.7.2 to latest and from Blog 4.5.2 to Blog 5.0. After the update, I'm seeing this error on any page where categories are displayed and in the admin when I click on Categories - Blog set.

Notice: Undefined index: catDepth in C:\Users\Clive Walker\Documents\Websites\Websites E-L\EICA 2011\perch\core\apps\categories\PerchCategories_Category.class.php on line 117

Is this because the category slug is 'blog' but on my site the blog pages are in the web space root?

My short diagnostic report

Perch: 2.8.19, PHP: 5.4.4, MySQL: mysqlnd 5.0.10 - 20111026 - $Id: b0b3b15c693b7f6aeb3aa66b646fee339f175e39 $, with PDO
Server OS: WINNT, apache2handler
Installed apps: content (2.8.19), assets (2.8.19), categories (2.8.19), perch_blog (5.0)
App runtimes: <?php $apps_list = array( 'content', 'categories', 'perch_blog', );
PERCH_LOGINPATH: /perch
PERCH_PATH: C:\Users\Clive Walker\Documents\Websites\Websites E-L\EICA 2011\perch
PERCH_CORE: C:\Users\Clive Walker\Documents\Websites\Websites E-L\EICA 2011\perch\core
PERCH_RESFILEPATH: C:\Users\Clive Walker\Documents\Websites\Websites E-L\EICA 2011\perch\resources
Image manipulation: GD
PHP limits: Max upload 32M, Max POST 32M, Memory: 128M, Total max file upload: 32M
Resource folder writeable: Yes
HTTP_HOST: eica.local
DOCUMENT_ROOT: C:/Users/Clive Walker/Documents/Websites/Websites E-L/EICA 2011
REQUEST_URI: /perch/core/settings/diagnostics/
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php