fix the 'add' module page javascript failing on Moodle 4.3+

[usqfowlerj]

Checklist

• the contributor license agreement is signed — the CLA URL is a 404 now, and I had signed it under a different github username anyway
• commit message follows commit guidelines
• screenshots are included showing significant UI changes — N/A
• documentation is changed or added — N/A

Description of change

From Moodle 4.3, YUI module moodle-core_availability-form now expects to find elements with ids fitem_id_availabilityconditionsjson and availabilityconditions-loading.

[edalex-ian]

Thanks for raising this @usqfowlerj , this unfortunately fell through our review processes. We'll schedule in some review and see if we can get this in.

[edalex-siddharth]

Thanks @usqfowlerj for providing a fix. I have a small suggestion for these changes to only add these elements when conditional access setting is enabled:

// When conditional access is enabled, moodle expects id_availabilityconditionsjson field, fitem_id_availabilityconditionsjson and availabilityconditions-loading in standard module form, as we don't use standard form.
 if(!empty($CFG->enableavailability)){
            echo html_writer::start_tag('form', array('style'=>'display:none'));
            echo html_writer::tag('div', '', array('id' => 'fitem_id_availabilityconditionsjson'));
            echo html_writer::tag('div', '', array('id' => 'availabilityconditions-loading'));
            echo html_writer::empty_tag('input', array('id'=>'id_availabilityconditionsjson', 'type'=>'hidden'));
            echo html_writer::end_tag('form');
            }