In the default course settings, numsections is not limited to maxsections

When controlling the maximum number of sections allowed in a course and the default number of sections in a new course, the number of sections should be limited by the maximum value.

Reproduction steps:

1. Log in as admin
2. Navigate to "Course default settings" (Settings -> Site administration -> Courses -> Course default settings)
3. Change "Maximum for number of weeks/topics moodlecourse | maxsections" to 0
4. Click save changes
5. Check "Number of weeks/topics moodlecourse | numsections" drop-down

Expected result: The number of weeks/topics should only show 0

Actual result: The number of weeks/topics shows numbers from 0 to 52

Currently the function that controls this value is in lib/adminlib.php...

class admin_settings_num_course_sections extends admin_setting_configselect {

    public function __construct($name, $visiblename, $description, $defaultsetting) {

        parent::__construct($name, $visiblename, $description, $defaultsetting, array());

    }

    /** Lazy-load the available choices for the select box */

    public function load_choices() {

        $max = get_config('moodlecourse', 'maxsections');

        if (empty($max)) {

            $max = 52;

        }

        for ($i = 0; $i <= $max; $i++) {

            $this->choices[$i] = "$i";

        }

        return true;

    }

}

The check to see if the maximum value is set fails to allow for a value of zero. Changing the check to use !isset() instead of empty resolves this.

if (!isset($max)) {