I have a building prefab with a script attached. When this prefab is instantiated I add it to a list. By clicking of this object, I access the attached script:

  hbScript = queryResult.SGobjectBuilding.GetComponent<SPHealthbar>();
   hbScript.showHB();

but sometimes I get a nullreference exception. My question, is there just one script in the scene? Because with show() I wanna activate a the healthbar of this particular building