I want to see the history of a wiki page to see who has contributed which content in order to grade the students wiki entries.
I use Moodle 2.0.1, Wiki in NWiki format and the history tab. For some pages the correct history list is displayed. For some pages I get the following error message (see attached file):

Notice: Trying to get property of non-object in /var/www/https/testMoodle201/mod/wiki/pagelib.php on line 1263
Created: Mittwoch, 16 Februar 2011, 04:06 by

Coding error detected, it must be fixed by a programmer: PHP catchable fatal error

The history functionality is critical in my opinion, without this feature I cannot grade student participation in the wiki activity.