Sticky Cube

So I am trying to make a sticky cube that I can pick up.

It has this script associated with it:

using UnityEngine; using System.Collections;

public class StickyObject : MonoBehaviour { FixedJoint joint; void Start () {

}

void Update () {
if (Input.GetKeyDown(KeyCode.Delete)) {
if (joint != null) {
Destroy(joint);
joint = null;
}
}
}
void OnCollisionEnter(Collision c)
{
joint = gameObject.AddComponent<FixedJoint>();
joint.connectedBody = c.rigidbody;

}

}

When I try to drop the cube it breaks the joint but it is still connected to the rigid body that picked it up, any ideas on how to destroy the joint?