title: How to activate trigger when gameObjects are destroyed?
body: <p>I want to activate/enable a TriggerCollider when the enemies in the area are killed. The enemies doesn't come in a certain order so can't add a script to a single enemy. 
  I created an empty game object and attached below (faulty) script. I want do <code>if( the public game objects are destroyed) activate trigger</code>. </p>
  
  <p>Would you know the correct for this?</p>
  
  <pre><code>public class ActivateDialogueTrigger : MonoBehaviour {
  
      public GameObject DialogueTrigger;
  
      public GameObject Enemy01;
      public GameObject Enemy02;
      public GameObject Enemy03;
      public GameObject Enemy04;
      public GameObject Enemy05;
      public GameObject Enemy06;
  
      void Start () {
  
          DialogueTrigger.SetActive(false);       
      }
  
  
      void Update () {
          if(gameobjects.destroyed){
  
              DialogueTrigger.SetActive(true);
          }
      }
  }
  </code></pre>