/// <summary>
 /// Adds an enemy to the list.
 /// </summary>
 public void AddEnemy(EnemyController enemy)
 {
     if (m_Enemies == null)
     {
         m_Enemies = new List<EnemyController>();
     }
     if (enemy != null)
     {
         enemy.SetHorde (this);
         m_Enemies.Add(enemy);
     }
 }
 /// <summary>
 /// Removes an enemy fron the list.
 /// </summary>
 public void RemoveEnemy(EnemyController enemy)
 {
     if (m_Enemies != null && enemy != null)
     {
         enemy.SetHorde (null);
         m_Enemies.Remove(enemy);
         if (m_Enemies.Count == 0)
         {
             Destroy(gameObject);
         }
     }
 }