Clicking add button when additionalProperties: true doesn't create a new property

[nickgros]

Prerequisites

• I have searched the existing issues
• I understand that providing a SSCCE example is tremendously useful to the maintainers.
• I have read the documentation
• Ideally, I'm providing a sample JSFiddle or a shared playground link demonstrating the issue.

What theme are you using?

core

Version

5.0.0-beta.10

Current Behavior

When additionalProperties: true, clicking the add button does not add a property.

I think this may be a regression from v4.

Expected Behavior

Clicking the button adds a property.

If it doesn't make sense to add a property, e.g. because there is no sensible default type, then the add button should not be shown, and a breaking change warning should be added to the v5.

Steps To Reproduce

Link to playground reproduction

Environment

Playground 5.0.0-beta.10

Anything else?

No response