Material doesn't have a texture property '_Maintex'

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class AnimatedMaterial : MonoBehaviour {

    private Renderer rend;
    private Material mat;
    private Color startEmissionColor;

    [SerializeField]
    private float offsetSpeed = 0.02f;
    [SerializeField]
    private float glowSpeed = 0.02f;


    // Use this for initialization
    void Start () {

        // get the renderer and material
        rend = GetComponent<Renderer> ();
        mat = rend.material;


        // Get this intial immision color
        startEmissionColor = mat.GetColor ("_EmissionColor");

        mat.SetColor ("_EmissionColor", startEmissionColor);

    }

    // Update is called once per frame
    void Update () {

        float offset = Time.time * offsetSpeed;
        mat.SetTextureOffset ("_Maintex", new Vector2(0, offset));

        float glow = Mathf.PingPong (Time.time * glowSpeed, 1f);
        mat.SetColor ("_EmissionColor", startEmissionColor * glow);
        DynamicGI.UpdateMaterials (rend);

    }
}