Raycast causes game to crash when shooting up

Okay, so right now I have a gun script that raycasts directly in front of the camera when the character shoots. Right now, it works fine when I shoot at something, but if I just look up and try to shoot at the sky the game crashes and says "NullReferenceException: Object reference not set to an instance of an object" even though I've used the same script several times without a problem. Here's what I have so far:

 var direction = this.transform.TransformDirection(Vector3.forward);
 var RayCastHit : RaycastHit;
 if (Physics.Raycast (transform.position, direction, RayCastHit, FireRange)) 
     {
         if (RayCastHit.rigidbody)
         {
             if (Weapon == "G36C")
             {
                     RayCastHit.rigidbody.AddForceAtPosition(150 * direction, RayCastHit.point);
             }
         }
     }
     if (RayCastHit.collider.gameObject.tag == "metal") 
         {                
             MetalParticle1.transform.position = RayCastHit.point;
             MetalParticle2.transform.position = RayCastHit.point;
             MetalParticle3.transform.position = RayCastHit.point;
             MetalParticle4.transform.position = RayCastHit.point;
             MetalParticle5.transform.position = RayCastHit.point;
             MetalParticle1.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             MetalParticle2.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             MetalParticle3.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             MetalParticle4.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             MetalParticle5.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             MetalParticle1.Emit();
             MetalParticle2.Emit();
             MetalParticle3.Emit();
             MetalParticle4.Emit();
             MetalParticle5.Emit();
             MetalParticle1.audio.Play();
             }
         else if (RayCastHit.collider.gameObject.tag == "concrete")
         {
             ConcreteParticle1.transform.position = RayCastHit.point;
             ConcreteParticle2.transform.position = RayCastHit.point;
             ConcreteParticle3.transform.position = RayCastHit.point;
             ConcreteParticle4.transform.position = RayCastHit.point;
             ConcreteParticle1.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             ConcreteParticle2.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             ConcreteParticle3.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             ConcreteParticle4.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             ConcreteParticle1.Emit();
             ConcreteParticle2.Emit();
             ConcreteParticle3.Emit();
             ConcreteParticle4.Emit();
             ConcreteParticle1.audio.Play();
         }
         else if (RayCastHit.collider.gameObject.tag == "wood")
         {
             WoodParticle1.transform.position = RayCastHit.point;
             WoodParticle2.transform.position = RayCastHit.point;
             WoodParticle3.transform.position = RayCastHit.point;
             WoodParticle4.transform.position = RayCastHit.point;
             WoodParticle1.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             WoodParticle2.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             WoodParticle3.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             WoodParticle4.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             WoodParticle1.Emit();
             WoodParticle2.Emit();
             WoodParticle3.Emit();
             WoodParticle4.Emit();
             WoodParticle1.audio.Play();
         }
         else if (RayCastHit.collider.gameObject.tag == "water")
         {
             WaterParticle1.transform.position = RayCastHit.point;
             WaterParticle2.transform.position = RayCastHit.point;
             WaterParticle3.transform.position = RayCastHit.point;
             WaterParticle1.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             WaterParticle2.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             WaterParticle3.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             WaterParticle1.Emit();
             WaterParticle2.Emit();
             WaterParticle3.Emit();
         }    
             else 
         {
             DirtParticle1.transform.position = RayCastHit.point;
             DirtParticle2.transform.position = RayCastHit.point;
             DirtParticle3.transform.position = RayCastHit.point;
             DirtParticle1.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             DirtParticle2.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             DirtParticle3.transform.rotation = Quaternion.FromToRotation(Vector3.up, RayCastHit.normal);
             DirtParticle1.Emit();
             DirtParticle2.Emit();
             DirtParticle3.Emit();
             DirtParticle1.audio.Play();
         }

When I double click the debug thing at the bottom, it highlights the line that says "if (RayCastHit.collider.gameObject.tag == "metal")".

Any help would be appreciated. Thanks