Correct Moodle 4.0 course renderer warning in frontpage

Now the course is rendered using output components there's an unexpected warning in the frontpage.

Notice: Undefined property: stdClass::$coursedisplay in course/classes/output/section_format/header.php on line 92

Steps to reproduce:

1. Set debug to developer level
2. Add some activity to the frontpage (not the dashboard, the old frontpage)
3. Edit summary (head section) and add a custom name.
4. Turn edit off

Expected result: no warning is displayed

Real result: in some instances, the $SITE course does not have 
$course->coursedisplay attribute an get a warning when the output component tries to access it.
 
How to solve: if "coursedisplay" is optional, output/header should take this into account. Apart, a behat test for this scenario will be a good idea.