Expected BEGIN_ARRAY but was STRING, how to convert the STRING to an empty ARRAY?

I'm doing a mobile application in Android/Java and I'm doing a few HTTP requests using Retrofit, RxJava and RxAndroid.

In one of those HTTP request, I have declared my model class to expect a response like this:

{
   "code":201,
   "message":"Successfully",
   "data":{
      "devices":[
         {
            "state":"OK",
            // ... a few more properties
         }
      ]
   }
}

There is a scenario where the same HTTP request return a different body, like this:

{
   "code":201,
   "message":"Successfully",
   "data":{
      "devices":"" // <= is not an array anymore, it's just an empty string
   }
}

Due to this difference in the response body I received the following error:

android Expected BEGIN_ARRAY but was STRING

I was thinking in a way to convert that empty string to an empty array to avoid the error, at least an empty array matches my model class.

My models:

public class FullResponse {
    @SerializedName("code")
    private int code;
    @SerializedName("message")
    private String message;
    @SerializedName("data")
    private FullData data;

    // Constructor
    // Getters & Setters
}

public class FullData {

    private List<Device> devices;

    // Constructor
    // Getters & Setters
}

public class Device {

    private String state;
    // ... a few more properties

    // Constructor
    // Getters & Setters
}

Interface of endpoints:

public interface ApiService {

    @FormUrlEncoded
    @POST("/status.php")
    Observable<FullResponse> getStatus(@HeaderMap Map<String, String> headers, @FieldMap Map<String, String> request);

}

Doing the request:

public class Request extends BaseRequest {

    private Map<String, String> requestData;
    private FullRequestSubscriber mStatusFullSubscriber;

    // Constructor

    @Override
    public void request() {
        HashMap<String, String> headers = new HashMap<>();
        headers.put("Content-Type", "application/x-www-form-urlencoded");

        if (mStatusFullSubscriber != null) {
                apiService
                        .getStatus(headers, requestData)
                        .subscribeOn(Schedulers.io())
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribe(mStatusFullSubscriber);
            }

        mStatusFullSubscriber.addToCompositeSubscription();

    }
}

Subscriber:

public class FullRequestSubscriber extends BaseSubscriber<FullResponse> {

    private FullResponse response;
    private Context mContext;
    private OnSubscriptionInteractionListener subscriptionListener;
    private OnRequestInteractionListener interactionListener;

    // Constructor

    @Override
    public void onStart() {
        this.response = null;
        super.onStart();
    }

    @Override
    public void onCompleted() {
        super.onCompleted();
        this.interactionListener.onRequestResponse(this.response);
    }

    // Error received here: android Expected BEGIN_ARRAY but was STRING
    @Override
    public void onError(Throwable e) {
        //super.onError(e);
        getSubscriberListener().removeSubscriber(this);

        if (requireLoading()) {
            ((BaseActivity) getContext()).hideLoading();
        }

        this.interactionListener.onRequestError();
    }

    @Override
    public void onNext(FullResponse o) {
        this.response = o;
    }

    @Override
    protected Context getContext() {
        return this.mContext;
    }

    @Override
    protected Class<?> getErrorResponseType() {
        return null;
    }

    @Override
    protected OnSubscriptionInteractionListener getSubscriberListener() {
        return this.subscriptionListener;
    }

    public interface OnRequestInteractionListener {
        void onRequestResponse(FullResponse data);
        void onRequestError();
    }
}

I'm not sure where and how can I do the conversion to fix the error.

My goal is to convert the empty string to an empty array to avoid the error and to maintain a matching model.