In admin/report/courseoverview/index.php, if the report doesn't generate any data (such as on our test server), you get some unneeded tags and some other junk (debugging message?).

The offending code is in that file on line 83 and is a whopping 3.5 years old: http://git.moodle.org/gw?p=moodle.git;a=commitdiff;h=e524c0ed56125ecdafd24f868848b9eebffc99f7

It looks like cvshead has it as well, on line 88.

You can remove everything after the call to notify() and it works just fine here.