Camera shake, everything disappear from screen except canvas.

I made camera shake script and when I use it on button everything except canvas disappear from screen (game is continue to go). I make 2d game and in game view option I set 9:14 (I tried with different views and there is same problem). Here is my code:

using UnityEngine; using System.Collections;

public class CameraShake : MonoBehaviour {

 public Camera mainCam;

 float shakeAmount = 0.2f;

 void Awake() {

     if (mainCam == null) {
         mainCam = Camera.main;
     }
 }
 void Update() {

     if (Input.GetKeyDown(KeyCode.T)) {

         Shake(0.1f, 0.1f);
     }
 }
 public void Shake (float amt, float length) {

     shakeAmount = amt;
     InvokeRepeating("BeginShake", 0.01f, 0);
     Invoke("StopShake", length);
 }

 void BeginShake() {

     if (shakeAmount > 0) {

         Vector3 camPos = mainCam.transform.position;

         float offsetX = Random.value * shakeAmount * 2 - shakeAmount;
         float offsetY = Random.value * shakeAmount * 2 - shakeAmount;
         camPos.x += offsetX;
         camPos.y += offsetY;

         mainCam.transform.position = camPos;
     }
 }

 void StopShake()
 {
     CancelInvoke("BeginShake");
     mainCam.transform.position = Vector3.zero;
 }

}

I set Camera as empty game object and MainCamera as child. Script is attached on child object.