iOS Swift (Xcode) - Initializing Class stops script without error (GMSCircle)

Question

I have a strange issue when trying to initialize a GMSCircle class from the Google Maps SDK.

I have this function in my MapViewController which contains a GMSMapView:

func createCircleOnMap(map: GMSMapView, circleCenter: CLLocationCoordinate2D, circleRadius: Double) {
    print("TEST 1")
    let addCircle = GMSCircle()
    print("TEST 2")
    addCircle.position = circleCenter
    addCircle.radius = circleRadius
    addCircle.map = map 
}

If I call this function from viewDidLoad() or the mapView delegate "didTapAtCoordinate", I can add a circle to the map without a problem.

However, if I call the function from a completion handler (in my case after returning information from AWS Lambda via the AWS SDK), I never get past the GMSCircle initialization.

This is my Lambda function:

func getMapData() {
    let json: NSDictionary = ["test" : "TEST"]

    let lambdaInvoker = AWSLambdaInvoker.defaultLambdaInvoker()
    lambdaInvoker.invokeFunction("MyLambdaFunction", JSONObject: json, completionHandler: { (response, err) -> Void in

        if (err != nil) {
            print("Error: \(err)")
        } else if (response != nil) {
            // PARSE THE JSON HERE

            self.createCircleOnMap(<#T##map: GMSMapView##GMSMapView#>, circleCenter: <#T##CLLocationCoordinate2D#>, circleRadius: <#T##Double#>)
        }

    })
}

The json parses fine (I checked those values), and when I pass it to createCircleOnMap, I get:

print("TEST 1")

in the console, but nothing else. It just stops without an error.

I also get the same result if I move the "addCircle" code to inside the Lambda function completion handler. My test print log "TEST 1" returns, but the script just stops without an error.

I also tried the initializer:

let addCircle = GMSCircle(position: circleCenter, radius: circleRadius)

with the same result.

I'm not even sure how to debug this issue. I've checked all the values, including sending hard-coded values to the function from inside the Lambda completion handler, and it still doesn't work. Maybe I just don't understand enough about Swift.

Any ideas?