[BUG] Curly Brace exception in sidecar if no HED

[VisLab]

Validator throws an exception for the following sidecar:

                  {
                        "event_code": {
                            "HED": {
                                "face": "Statistical-accuracy/0.677, {response}"
                            }
                        },
                        "response": "Label/#"
                        }
                    }

It should report a validator error rather than throwing an exception. The "HED" is missing from response.