3D infinite runner game platform generation gives an error

Situation: I am referring to http://catlikecoding.com/unity/tutorials/runner/ tutorial for my project,and there is an object pooling concept within the code

Problem: What happens is , after i scripting the generation platform(PlatformManager.cs), i get an exceptions saying,

InvalidOperationException: Operation is not valid due to the current state of the object System.Collections.Generic.Queue`1[UnityEngine.Transform].Peek () PlatformManager.Update () (at Assets/Platform/PlatformManager.cs:35)

PlatformManager.cs script:

  using UnityEngine;
     using System.Collections;
     using System.Collections.Generic;
     
     public class PlatformManager  : MonoBehaviour {
         public Transform prefab;
         public int numberOfObjects;
         public float recycleOffset;
         public Vector3 startPosition;
         public Vector3 minSize, maxSize,minGap, maxGap;
         public float minY, maxY;
     private Vector3 nextPosition;
         private Queue<Transform> objectQueue;
         void Start () {
             objectQueue = new Queue<Transform>(numberOfObjects);
             for (int i = 0; i < numberOfObjects; i++) {
                 objectQueue.Enqueue((Transform)Instantiate(prefab));
             }
             nextPosition = startPosition;
             for (int i = 0; i < numberOfObjects; i++) {
                 Transform o = (Transform)Instantiate(prefab);
                 o.localPosition = nextPosition;
                 nextPosition.x += o.localScale.x;
                 objectQueue.Enqueue(o);
             }
         }
         void Update () {
           //FOLLOWING LINE IS THE 35TH LINE
             if (objectQueue.Peek().localPosition.x + recycleOffset < Runner.distanceTraveled) {  
                 Transform o = objectQueue.Dequeue();
                 o.localPosition = nextPosition;
                 nextPosition.x += o.localScale.x;
                 objectQueue.Enqueue(o);
                 Recycle();
             }
         }    
         private void Recycle () {
         Vector3 scale = new Vector3(
                 Random.Range(minSize.x, maxSize.x),
                 Random.Range(minSize.y, maxSize.y),
                 Random.Range(minSize.z, maxSize.z));
             Vector3 position = nextPosition;
             position.x += scale.x * 0.5f;
             position.y += scale.y * 0.5f;
             Transform o = objectQueue.Dequeue();
             o.localScale = scale;
             o.localPosition = position;
             nextPosition.x += scale.x;
             objectQueue.Enqueue(o);
             nextPosition += new Vector3(
                 Random.Range(minGap.x, maxGap.x) + scale.x,
                 Random.Range(minGap.y, maxGap.y),
                 Random.Range(minGap.z, maxGap.z));
             if(nextPosition.y < minY){
                 nextPosition.y = minY + maxGap.y;
             }
             else if(nextPosition.y > maxY){
                 nextPosition.y = maxY - maxGap.y;
             }
         }
     }