error code cs1061 'material does not contain definition for Main texture offset'

I’m having trouble with making a moving track. how do i put a definition in material

using UnityEngine;
using System.Collections;

public class TrackMove : MonoBehaviour {

public float speed;
Vector2 offset;

// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {
offset = new vector2 (0, Time.time * speed);
GetComponent().material.MainTextureOffset = offset;
}
}