I upgraded from Moodle 1.9 to 2.1 and now I can't see participants anymore. The error is shown in the picture below.

I do not use any plugins.

This Issue is different from http://tracker.moodle.org/browse/MDL-31258 since I did not upgrade from 1.8 but from 1.9 .

Also here someone reported the same bug in Moodle 2.2 http://moodle.org/mod/forum/discuss.php?d=194099.

I tried upgrading again from 2.1 to 2.2 so that the error might dissapear, but before even upgrading I receive an error message on top of the index.php:

Notice: Undefined property: stdClass::$defaulthomepage in /****/moodle/index.php on line 46