RestAssured Json response verification with GPath

I receive the following response on a bad request against my API. I am using RestAssured for my rest response assertions.

{
    "message": "An entity of type topic was passed in an invalid format",
    "meta": {
        "display": {
            "topic": [
                {
                    "name": [
                        "must not be blank"
                    ]
                },
                {
                    "contentType": [
                        "must not be blank"
                    ]
                },
                {
                    "content": [
                        "must not be blank"
                    ]
                },
                {
                    "version": [
                        "must not be blank"
                    ]
                }
            ]
        }
    }
}

I need to verify value of all the properties of the response. I am struggling to verify this path: meta.display.topic.contentType. I cannot come up with the GPath for it.

Here is the assertion that I am making:

given().body("{}").when()
            .post(BASE_URL)
            .prettyPeek()
            .then()
            .statusCode(400)
            .contentType(ContentType.JSON)
            .body("message", is("An entity of type topic was passed in an invalid format"),
                    "meta.display.topic.contentType", is("must not be blank"));

Since the path is not correct, assertion always fails.

To avoid hardcoded array positions for topic object following will work:

meta.display.topic.find { it.contentType != null }.contentType[0]