Upload multiple 'Revert to draft' button redirects to wrong page

In file '/mod/assignment/type/upload/assignment.class.php', in the function 'unfinalize()', the following line seems to cause a problem:

$returnurl = "submissions.php?id={$this->cm->id}&userid=$userid&mode=$mode&offset=$offset&forcerefresh=1";

This seems to redirect the page to a URL which still has the '&'s hard coded into it, rather than replaced by '&'. This causes the 'view all submissions' page to be displayed in the window, rather than continuing to show the 'view single submission' page.

Suggested fix - change the line in question to:

$returnurl = new moodle_url('/mod/assignment/submissions.php', array('id'=>$this->cm->id, 'userid'=>$userid, 'mode'=>$mode, 'offset'=>$offset, 'forcerefresh'=>1) );