Leap Motion-Beginner Scripting Issues

I am very new to all things Unity and C#, so bear with me. I've been trying to work with some of the scripts in the demos that come with the "Leap Motion Core Assets" from the Unity store. Specifically the ChangeMaterialOnGrab. I have made the script a component of the object, and applied the Changing Object and Grabbed Material, but this Error keeps coming up. I have made no edits to the code which was included in the package. "

NullReferenceException: Object reference not set to an instance of an object ChangeMaterialOnGrab.Update () (at Assets/LeapMotion/DemoResources/Scripts/ChangeMaterialOnGrab.cs:34)

This is the part of the code that I think it is referring to.

  void Update() {
     bool grabbed = GetComponent<GrabbableObject >().IsGrabbed();
     if (grabbed && !grabbed_)
       OnGrab();
     else if (!grabbed && grabbed_)
       OnRelease();

I know it means something is wrong with line 34, but I guess I am not versed well enough with either the Leap Motion or C# to know what exactly it is. Any advice would be greatly appreciated!