object referance problem with bullet adding

i keep getting the following error
NullReferenceException: Object reference not set to an instance of an object
heatSeakingProjectile.Update () (at Assets/Scripts/GamePlay/heatSeakingProjectile.cs:27)

void Update ()
{
	if (Input.GetMouseButton (0)) { 			
		foreach (Transform child in transform) {
			if (child.tag == "heatSeak") {
                Rigidbody clone;
				 clone = Instantiate (Resources.Load ("gamePlay/heatSeak"), child.position, child.rotation)as Rigidbody;
				print(clone.velocity);// error occurring here
			}
		}
	}
}

This line of code is where the error actually start:

 clone = Instantiate (Resources.Load ("gamePlay/heatSeak"), child.position, child.rotation)as Rigidbody;

What type of asset are you trying to instantiate?
Isn’t heatSeak a Game Object?

Could it be that heatSeak is a gameObject with a RigidBody on it?

I also suggest you do this:

    private GameObject heatSeakPrefab;
	
	void Start()
	{
		heatSeakPrefab = Resources.Load ("gamePlay/heatSeak", typeof(GameObject)) as GameObject;
	}
	
	
	void Update()
	{
		if (Input.GetMouseButton (0)) 
		{       
			foreach (Transform child in transform) 
			{
				if (child.CompareTag("heatSeak") )
				{
					Rigidbody clone;
					clone = Instantiate (heatSeakPrefab, child.position, child.rotation)as Rigidbody;
					print(clone.velocity);// error occurring here
         		}
       		}
    	}
	}