Object Reference Not Set to an Instance of an object

Keep getting this error in line.SetPosition(1, bob.transform.position); can someone help me fix this? this code is just to draw a grappling hook line from the shooter to a designated distance.

 // Line start width
 var startWidth = 0.05;
 // Line end width
 var endWidth = 0.05;
 //or you could use...
 //var aMaterial : Material;
 
 
 // get line going...
 private var line : LineRenderer;
 
 function Start ()
 {
    line = this.gameObject.AddComponent(LineRenderer);
    line.SetWidth(startWidth, endWidth);
    line.SetVertexCount(2);
    line.material.color = Color.black;
 //we need to see the line... 
    line.renderer.enabled = true;
 }
 
 function Update ()
 {
 //get the shooter object...
 bob = GameObject.Find("Shooter");
 //set starting point of line to this object, in this case the grappling hook prefab
    line.SetPosition(0, this.gameObject.transform.position);
 //set the ending point of the line to the shooter object
    line.SetPosition(1, bob.transform.position);
 }