Android touch input Null Reference exception error

I am trying to make a car racing game . In this game I have made two Buttons and attached scripts carController to its EventTrigger on pointer down as follows :

the car controller script is in c# and is as follows:

   public class carController : MonoBehaviour {
         public float carSpeed;
         Vector3 position;
         public uiManager ui;
         public audioManager am;
      Rigidbody2D rb;
         bool currentPlatformAndroid=false;
         // Use this for initialization
     
         void awake(){
     
             rb = GetComponent<Rigidbody2D> ();
             #if  UNITY_ANDROID
             currentPlatformAndroid=true;
             #else
             currentPlatformAndroid=false;
             #endif
             am.carSound.Play ();
     
         }
     
     
         void Start () {
             //ui = GetComponent<uiManager> (); no need
     
             if (currentPlatformAndroid == true) {
     
                 Debug.Log ("Android");
             } else {
                 Debug.Log ("windows");
             }
     
             position = transform.position;
         }
         
         // Update is called once per frame
         void Update () {
             if (currentPlatformAndroid == true) {
                 //android specific
                 TouchMove();
     
             } else {
                 position.x+=Input.GetAxis ("Horizontal") * carSpeed * Time.deltaTime;
                 position.x= Mathf.Clamp (position.x, -2.1f, 2.1f);
                 transform.position = position;
             }
             position = transform.position;
             position.x= Mathf.Clamp (position.x, -2.1f, 2.1f);
             transform.position = position;
     
     
     
         }
     
         void OnCollisionEnter2D(Collision2D col){
     
             if (col.gameObject.tag == "Enemy Car") {
                 gameObject.SetActive (false);
                 ui.gameOverF ();
                 am.carSound.Stop ();
             }
     
         }
     
         public void MoveLeft(){
             rb.velocity = new Vector2 (-carSpeed, 0);
         }
     
         public void MoveRight(){
             rb.velocity = new Vector2 (carSpeed, 0);
         }
     
         public void SetVelocityZero(){
     
             rb.velocity = Vector2.zero;
         }
     
         void TouchMove(){
             if (Input.touchCount > 0) {
                 Touch touch = Input.GetTouch (0);
                 float middle=Screen.width/2;
                 if (touch.position.x < middle && touch.phase == TouchPhase.Began) {
                     MoveLeft ();
                 }
                 else if((touch.position.x > middle && touch.phase == TouchPhase.Began)){
                     MoveRight();
                 }
                     
                     
     
                     }else{
                         SetVelocityZero();
                     }
     
     
     
         }
     
     
     }

Now I have tried both button touch and swipe touch but both are not working !!

Am I am not able to figure out why ?

Can anybody help ?