(SOLVED) How can I prevent " index was out of range" error on this script?

I'm trying to find a way to prevent an "index was out of range" error in update when there aren't any targets to find.
I thought I could add an if statement to return if there weren't any "selected objects," but I'm still encountering the error.

Code (CSharp):

1.  using UnityEngine;
2. using System.Collections;
3. using System.Collections.Generic;
4. public class AI_FindObjects : MonoBehaviour {
5.  
6.      public List <Transform> Enemies;
7.      public Transform SelectedTarget;
8.  
9.      void Update ()
10.      {
11.  
12.          SelectedTarget = null;
13.          Enemies = new List<Transform>();
14.          AddEnemiesToList();
15.      
16. }
17.      public void AddEnemiesToList()
18.      {
19.          GameObject[] ItemsInList = GameObject.FindGameObjectsWithTag("PitcherPlant");
20.          foreach(GameObject _Enemy in ItemsInList)
21.          {
22.              AddTarget(_Enemy.transform);
23.          }
24.      }
25.      public void AddTarget(Transform enemy)
26.      {
27.          Enemies.Add(enemy);
28.      }
29.      public void DistanceToTarget()
30.      {
31.          Enemies.Sort(delegate( Transform t1, Transform t2){
32.              return Vector3.Distance(t1.transform.position,transform.position).CompareTo(Vector3.Distance(t2.transform.position,transform.position));
33.          });
34.      }
35.      public void TargetedEnemy()
36.      {
37.          if(SelectedTarget == null)
38.          {
39.              DistanceToTarget();
40.              SelectedTarget = Enemies[0];
41.          }
42.      }
43.      void LateUpdate ()
44.      {
45.          TargetedEnemy();
46.          float dist = Vector3.Distance(SelectedTarget.transform.position,transform.position);
47.           transform.position = Vector3.Lerp (transform.position, SelectedTarget.position, Time.deltaTime*1);
48.      }
49. }
50.  
51.  

 

Here are some notes on IndexOutOfRangeException and ArgumentOutOfRangeException:

http://plbm.com/?p=236

First, find where the out of range is happening.

Second, find why

Third, fix that.

 

Thanks, Kurt,
I found where the error is coming from- which is the "Enemies" in the above list.
And the why- there aren't any "Enemies" in the scene at runtime.
What I'm not understanding is how to check if there are no Enemies, and prevent this exception error.

 

The only dereference I see is line 40 above... you are hard-wiring and grabbing the first one (element zero).

Don't do that if there isn't anything in the list. Collections such a list have a .Count property you can check to make sure it's greater than zero, and Arrays use the .Length property instead.

 

Something you can do to improve your script (as you're creating a new List every frame) is clear it instead:
- Change line 6 to:

public List<Transform> Enemies = new List<Transform>();

- Change line 13 to:

Enemies.Clear();

 

And as Kurt mentioned, you can dodge the error in line 40 by changing line 37 to..

if ((SelectedTarget == null) && (Enemies.Count != 0))

..and after line 45, you should add..

if (SelectedTarget == null) return;

 

Thanks, Polemical- that sorted the issue out, grateful for the help.
Also, thanks for showing me the reason behind this error, Kurt- much appreciated!