NullReferenceException: Object reference not set to an instance of an object pictureFactory.CreateIm

Hi guys,
i am new to unity and AR and for my thesis im trying to build an AR google Museum using unity 3D and vuforia ground plane stage where i project images from google using rest protocoll and google custom searh api and projecting the pictures with vuforia fround plane stage.

I get this error :
NullReferenceException: Object reference not set to an instance of an object
pictureFactory.CreateImages (System.Collections.Generic.List`1[T] urlList, System.Int32 resultNum, UnityEngine.Vector3 camForward) (at Assets/scripts/pictureFactory.cs:35)
GoogleService+<<GetPicture>g__PictureRoutine|3_0>d.MoveNext () (at Assets/scripts/GoogleService.cs:51)


This is Google service script where the function is called:

Vector3 cameraForward = Camera.main.transform.forward;

       

int RowNum = 1;

for( int i = 0 ; i <= 9 ;  i=i+2) {



    string url= "https://customsearch.googleapis.com/customsearch/v1?cx=c52e7231e56d59bd3&exactTerms=" + query +

     "&filter=1&num=10&searchType=image&start=" + i + "&fields=items%2Flink&key=" + API_KEY;





        UnityWebRequest reg = new UnityWebRequest(url);

        reg.downloadHandler = new DownloadHandlerBuffer();



        yield return reg.SendWebRequest();

   

Debug.Log(reg.downloadHandler.text);



List<string> links= ParseResponse(reg.downloadHandler.text);

Debug.Log(links[9]);

pictureFactory.CreateImages(ParseResponse(reg.downloadHandler.text) , RowNum, cameraForward);

RowNum++;

}

This is my Createimages function:

 public void CreateImages(List <string> urlList, int resultNum , Vector3 camForward) {

        int PicNum=1;

        Vector3 center = Camera.main.transform.position;

    foreach (string url in urlList){

       Vector3 pos= GetPosition (PicNum, resultNum, camForward);

        GameObject pic= Instantiate(PicPrefab , pos , Quaternion.identity ,this.transform);

pic.GetComponent<pictureBehaviour>().LoadImage(url);

PicNum++;

    }

the LoadImage function is:

StartCoroutine(LoadImageFromURL (url));



        }

        IEnumerator LoadImageFromURL(string url)  {

           

        using (UnityWebRequest loaded = UnityWebRequestTexture.GetTexture(url))

        {

            yield return loaded.SendWebRequest();



            if (loaded.result != UnityWebRequest.Result.Success)

            {

                Debug.Log(loaded.error);

            }

            else

            {

                 Debug.Log(url);

               

                 quadRenderer.material.mainTexture = DownloadHandlerTexture.GetContent(loaded);

               

            }

        }

I dont really understand what parameter is not taken by the function or is wrong can someone please help.