new index error after upgrading from 4.0.0 to 4.0.7

I'm responding to Hershel's request to report this apparent issue for discussed here:
http://forum.civicrm.org/index.php/topic,22113.msg92632.html#msg92632

In the older 4.0.0 version of CiviCRM I was using, I did not have a "order by" option in my Activities report. When I upgraded to 4.0.7 and set the option in a report and saved the report, I received this new error repeated twice in red:

Notice: Undefined index: section in CRM_Report_Form->orderBy() (line 1788 of /var/www/drupal-7.0/sites/all/modules/civicrm/CRM/Report/Form.php).

Despite the error, the report did change order correctly. The related dashlet still appears to work. Returning to generate the report from the report menu recreates the error message.