How do I check if a game object exists?

Hello. I'm trying to run a check for null before the object "shotSaw" is removed. There are multiple things that can destroy the saw, so I need to make sure scripts do not error when there is no saw to delete. However, checking for null still doesn't prevent the error. Is this a problem with my logic, or should I check for something besides null?

 var force : int;
 var shootPosition:Transform;
 var charging : boolean;
 var shotSaw : GameObject;
 var idleSound : AudioClip;
 var shotSound : AudioClip;
 var spinSpeed : float;
 
 function Start () {
 
 }
 
 function FixedUpdate () 
 {
 print (shotSaw.transform.localScale.x);
 if (Input.GetButton ("Fire1")) 
     {
     if (charging != true)
         {
         shotSaw = Instantiate (saw, transform.position, shootPosition.rotation);
         charging = true;
         }
     if (charging == true)
         {
         if(!audio.isPlaying)
             {
             audio.PlayOneShot(idleSound);
             audio.Play();
             }
         if (shotSaw != null)
                     {
                     shotSaw.rigidbody2D.AddTorque (spinSpeed/2);
                     shotSaw.rigidbody2D.gravityScale = 0;
                     shotSaw.collider2D.isTrigger = true;
                     shotSaw.transform.position = Vector3(shootPosition.position.x,shootPosition.position.y,shootPosition.position.z);
                     }
         }
     }
     else
     {
         if (charging == true)
         {
         if (shotSaw != null)
             {
             if (shotSaw.transform.localScale.x > 0.0280)
                 {
                 audio.Stop();
                 shotSaw.rigidbody2D.gravityScale = 1;
                 shotSaw.collider2D.isTrigger = false;
                 shotSaw.rigidbody2D.AddForce(shootPosition.right * force);
                 charging = false;
                 audio.Stop();
                 }
                 else
                 {
                     if (shotSaw != null)
                     {
                     Destroy(shotSaw);
                     }
                 }
             }
         }
     }
 }

Any help would be appreciated.