Removing value of required sdc component property causes fatal error when "x-canvas-group" is set on the property

Problem/Motivation

Removing value of required sdc component property causes fatal error.

Steps to reproduce

- Add "x-canvas-group: content" (or style, etc.) to a required component property (e.g. inside "byte_theme", "heading.component.yml", "heading_text").
- Go to the component settings on the UI and empty the property value of this required property ("Heading Text"):

- Resulting in an error on the settings page, making the entire component unusable, since the input for readding the required input is gone entirely:

Proposed resolution

Without the "x-canvas-group" key, it works as expected, so we should identify the problem and fix it.

Workaround

For properties in x-canvas-group: content simply remove this line, as content is the default anyway. This workarounds the issue.
For properties in style, etc. this doesn't work of course.

Remaining tasks

User interface changes

API changes

Data model changes