default values displayed incorrectly as "[object Object]"

[dquig]

Describe the bug

In 2.1.x, the following request body

{
    "Observation": {
        "title": "Thing",
        "required": [
            "fields",
            "id"
        ],
        "type": "object",
        "properties": {
            "fields": {
                "title": "Fields",
                "type": "object",
                "additionalProperties": {
                    "anyOf": [
                        {
                            "type": "number"
                        },
                        {
                            "type": "array",
                            "items": {
                                "type": "number"
                            }
                        }
                    ]
                },
            },
            "meta": {
                "title": "Meta",
                "allOf": [
                    {
                        "$ref": "#/components/schemas/ThingMeta"
                    }
                ],
                "description": "Thing metadata.",
                "default": {
                    "properties": {}
                }
            },
            "id": {
                "title": "Id",
                "type": "string",
                "description": "Unique id of the Thing."
            }
        }
    }
}

Renders like

Expected behavior

2.0.0 renders the meta field as expected

Minimal reproducible OpenAPI snippet(if possible)

Provided inline

Screenshots

Provided inline

Additional context