Modified Rigidbody throw causing errors

I took this modified rigidbody throw script and modified it some more, and everytime I throw an object I get an error.

Code:

Code (csharp):

1. var normalCollisionCount = 1;
2. var spring = 50.0;
3. var damper = 5.0;
4. var drag = 10.0;
5. var angularDrag = 5.0;
6. var distance = 0.2;
7. var throwForce = 500;
8. var throwRange = 1000;
9. var attachToCenterOfMass = false;
10. var handgui : GameObject;
11.  
12. private var springJoint : SpringJoint;
13.  
14. function Update ()
15. {
16.     var mainCamera = FindCamera();
17.         var hit : RaycastHit;
18.  
19.  
20.     if (Physics.Raycast(mainCamera.ScreenPointToRay(Input.mousePosition),  hit, 3))
21.     {
22.         if (hit.rigidbody  !Input.GetMouseButton (0))
23.         handgui.guiTexture.enabled = true;
24.         else
25.         handgui.guiTexture.enabled = false;
26.     }
27.     else
28.     handgui.guiTexture.enabled = false;
29.  
30.  
31.     // Make sure the user pressed the mouse down
32.     if (!Input.GetMouseButtonDown (0))
33.         return;
34.  
35.  
36.  
37.     // We need to actually hit an object
38.  
39.     if (!Physics.Raycast(mainCamera.ScreenPointToRay(Input.mousePosition),  hit, 3))
40.         return;
41.        
42.     // We need to hit a rigidbody that is not kinematic
43.     if (!hit.rigidbody || hit.rigidbody.isKinematic)
44.         return;
45.  
46.     if (!springJoint)
47.     {
48.         var go = new GameObject("Rigidbody dragger");
49.         var body : Rigidbody = go.AddComponent ("Rigidbody") as Rigidbody;
50.         springJoint = go.AddComponent ("SpringJoint");
51.         body.isKinematic = true;
52.     }
53.  
54.     springJoint.transform.position = hit.point;
55.     if (attachToCenterOfMass)
56.     {
57.         var anchor = transform.TransformDirection(hit.rigidbody.centerOfMass) + hit.rigidbody.transform.position;
58.         anchor = springJoint.transform.InverseTransformPoint(anchor);
59.         springJoint.anchor = anchor;
60.     }
61.     else
62.     {
63.         springJoint.anchor = Vector3.zero;
64.     }
65.  
66.     springJoint.spring = spring;
67.     springJoint.damper = damper;
68.     springJoint.maxDistance = distance;
69.     springJoint.connectedBody = hit.rigidbody;
70.  
71.        
72.     StartCoroutine ("DragObject", hit.distance);
73. }
74.  
75. function DragObject (distance : float)
76. {
77.        
78.    
79.     var oldDrag = springJoint.connectedBody.drag;
80.     var oldAngularDrag = springJoint.connectedBody.angularDrag;
81.     springJoint.connectedBody.drag = drag;
82.     springJoint.connectedBody.angularDrag = angularDrag;
83.     var mainCamera = FindCamera();
84.     while (Input.GetMouseButton (0))
85.     {
86.         var ray = mainCamera.ScreenPointToRay (Input.mousePosition);
87.         springJoint.transform.position = ray.GetPoint(distance);
88.         yield;
89.  
90.         if (Input.GetMouseButton (1)){
91.             springJoint.connectedBody.AddExplosionForce(throwForce,mainCamera.transform.position,throwRange);
92.             springJoint.connectedBody.drag = oldDrag;
93.             springJoint.connectedBody.angularDrag = oldAngularDrag;
94.             springJoint.connectedBody = null;
95.         }
96.     }
97.     if (springJoint.connectedBody)
98.     {
99.         springJoint.connectedBody.drag = oldDrag;
100.         springJoint.connectedBody.angularDrag = oldAngularDrag;
101.         springJoint.connectedBody = null;
102.     }
103.    
104.    
105. }
106.  
107. function FindCamera ()
108. {
109.     if (camera)
110.         return camera;
111.     else
112.         return Camera.main;
113. }

Error:

Any help would be greatly appreciated,

 

Something is null..
Try finding it with Debug.Log (add before the line 91)

for example,

Code (csharp):

1. Debug.Log(springJoint.name);
2. Debug.Log(mainCamera.transform.position);