MDL-82260 course: add hidden course field to edit section form

A course id hidden field is needed to edit availability conditions
directly from behat. This fields is not relevant to normal execution but
it is not harmfull as section update will ignore it.

course/editsection_form.php

@@ -47,6 +47,9 @@ class editsection_form extends moodleform {
         $mform->addElement('hidden', 'id');
         $mform->setType('id', PARAM_INT);
 
+        $mform->addElement('hidden', 'course', 0);
+        $mform->setType('course', PARAM_INT);
+
         // additional fields that course format has defined
         $courseformat = course_get_format($course);
         $formatoptions = $courseformat->section_format_options(true);