Actor not in world

public class Enemy2 extends Enemy
{
    int timesHit=2;
    /**
     * Act - do whatever the Enemy2 wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act() 
    {
        moveEnemy();
        removeEnemy();
        hitByProjectile();
    } 
    public void hitByProjectile()
    {
       Actor projectile = getOneIntersectingObject(Projectile.class);
       if (projectile != null)
       {
         getWorld().removeObject(projectile);
         timesHit--;
       }
       if (timesHit == 0)
       {
          getWorld().removeObject(this); 
       }
    }
}