Setting up an array property in "Fixed Values" doesn't work.

Problem/Motivation

I have a component that has an array property. If I activate the SDC display in a content type display and try to set a fixed value by clicking on "Append an item", an Ajax error occurs.
Warning: Trying to access array offset on null in /var/www/html/vendor/e0ipso/schema-forms/src/Drupal/FormGeneratorDrupal.php on line 277

Debuging the code, the function addMoreAjax tries to find the element $form["sdc_display"]["mappings"]["static"]["props"]["custom_card_classes"] in the $form but that doesn't exist.

Steps to reproduce

1. Create a component that has a property type: array
2. Go to a Content Type and activate the Render using a component
3. Expand the Fixed Values and click on Append an item in your array property

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes