Texture2D is Null even though hooked up in Inspector.

I am trying to draw a 2D texture as part of a reticule in my game. I have a Texture2D in my script and have it hooked up to a png in the inspector. When I try to use it I just get Null reference exceptions. I can programatically make a texture which works and I can see the quad I want but I want to use the png texture. This is the basics of what I have: public class Ship : MonoBehaviour { public Texture2D crosshair;

 Texture2D sameTeamTexture;
 Texture2D enemyTeamTexture;

 void Start()
 {
     /*sameTeamTexture = new Texture2D(10, 10);    
     for(int i =0; i < sameTeamTexture.width; ++i)
     {
         for(int j=0; j < sameTeamTexture.height; ++j)
         {
             sameTeamTexture.SetPixel(i, j, new Color( 1, 1, 1, 1 ) );
         }
     }
     sameTeamTexture.Apply();
     
     enemyTeamTexture = new Texture2D(10, 10);    
     for(int i =0; i < enemyTeamTexture.width; ++i)
     {
         for(int j=0; j < enemyTeamTexture.height; ++j)
         {
             enemyTeamTexture.SetPixel(i, j, new Color( 1, 0, 0, 1 ) );
         }
     }
     enemyTeamTexture.Apply();*/
 }
 
 void OnGUI()
 {
     DrawCrosshair( Vector3.zero, 100.0f, true, false );
     
     var players = PlayerTracker.GetAllPlayerInfos();
     var myPlayerInfo = PlayerTracker.MyPlayerInfo;
     foreach( PlayerInfo player in players )
     {
         if ( player != myPlayerInfo )
         {
             Vector3 screenPos = Camera.mainCamera.WorldToScreenPoint( player.transform.position );
             float border = 100.0f;
             DrawCrosshair( screenPos, border, false, player.PlayerTeam == myPlayerInfo.PlayerTeam );
         }
     }
 }
 
 private void DrawCrosshair( Vector3 screenPos, float border, bool drawWhenVisible, bool sameTeam )
 {
     // snap position and display texture
     screenPos.x = Mathf.Clamp( screenPos.x, border, Camera.mainCamera.GetScreenWidth() - border );
     screenPos.y = Mathf.Clamp( screenPos.y, border, Camera.mainCamera.GetScreenHeight() - border );
     
     /* debug - draw quad
     Texture2D tex;
     if ( sameTeam )
     {
         GUI.color = new Color( 1, 1, 1, 1 );
         tex = sameTeamTexture;
     }
     else
     {
         GUI.color = new Color( 1, 0, 0, 1 );
         tex = enemyTeamTexture;
     }
     GUI.DrawTexture(new Rect( screenPos.x,
                          Camera.mainCamera.GetScreenHeight() - screenPos.y, 
                         tex.width,
                         tex.height), 
                         tex, ScaleMode.StretchToFill, false);*/
                         
     GUI.DrawTexture(new Rect( screenPos.x - (crosshair.width * 0.5f),
                          screenPos.y - (crosshair.height * 0.5f), 
                         crosshair.width,
                         crosshair.height), 
                         crosshair, ScaleMode.ScaleToFit, false);
 }

What am I failing to do to get this working? Thanks Allan