i have added an object but its not appearing in the game

this is the error am getting

NullReferenceException: Object reference not set to an instance of an object InfiniteRunner.InfiniteObjects.InfiniteObject.SetParent (UnityEngine.Transform parent) (at Assets/Infinite Runner/Scripts/InfiniteObjects/InfiniteObject.cs:112) InfiniteRunner.InfiniteObjects.CollidableObject.SetParent (UnityEngine.Transform parent) (at Assets/Infinite Runner/Scripts/InfiniteObjects/CollidableObject.cs:68) InfiniteRunner.InfiniteGenerator.InfiniteObjectManager.AssignParent (InfiniteRunner.InfiniteObjects.InfiniteObject infiniteObject, ObjectType objectType) (at Assets/Infinite Runner/Scripts/InfiniteGenerator/InfiniteObjectManager.cs:271) InfiniteRunner.InfiniteGenerator.InfiniteObjectManager.ObjectFromPool (Int32 localIndex, ObjectType objectType) (at Assets/Infinite Runner/Scripts/InfiniteGenerator/InfiniteObjectManager.cs:250) InfiniteRunner.InfiniteGenerator.InfiniteObjectGenerator.SpawnCollidable (ObjectType objectType, Vector3 position, Vector3 direction, ObjectLocation location, InfiniteRunner.InfiniteObjects.PlatformObject platform, Int32 platformLocalIndex, Boolean activateImmediately) (at Assets/Infinite Runner/Scripts/InfiniteGenerator/InfiniteObjectGenerator.cs:384) InfiniteRunner.InfiniteGenerator.InfiniteObjectGenerator.SpawnObjects (ObjectLocation location, Vector3 position, Vector3 direction, Boolean activateImmediately) (at Assets/Infinite Runner/Scripts/InfiniteGenerator/InfiniteObjectGenerator.cs:261) InfiniteRunner.InfiniteGenerator.InfiniteObjectGenerator.SpawnObjectRun (Boolean activateImmediately) (at Assets/Infinite Runner/Scripts/InfiniteGenerator/InfiniteObjectGenerator.cs:180) InfiniteRunner.InfiniteGenerator.InfiniteObjectGenerator.Start () (at Assets/Infinite Runner/Scripts/InfiniteGenerator/InfiniteObjectGenerator.cs:98)