Error #2006: The supplied index is out of bounds - indexing

Question

I keep getting
Error #2006: The supplied index is out of bounds.
at flash.display::DisplayObjectContainer/getChildAt()
at Main/onFrame()
This is mostly referring to this part of my code
else if (comp) //if completion is true
{
var animation = char.getChildAt(2); //
if (animation.currentFrame == animation.totalFrames)
{
animation.stop();
addChild(end);
My animation that I am pulling at the second frame also isn't running at all, though I have checked the symbol and the frames within it, and it should work fine. I'm pretty new to code and this is what I have been taught so far.
This is the rest of my code here.
We are supposed to make a basic game where our character walks to a power up and does a power up animation, followed by an end game title.
package
{
import flash.display.MovieClip;
import fl.motion.easing.Back;
import flash.sampler.Sample;
import flash.events.Event;
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;
public class Main extends MovieClip
{
var bg:Background;
var b:Bubbles;
var b2:Bubbles;
var s:Seaweed;
var pressingRight:Boolean = false;
var pressingLeft:Boolean = false;
var comp:Boolean = false;
var speed:int = 10;
var char:Character;
var pu:PowerUp;
var hit:hit1
var end:EndGame;
public function Main()
{
bg = new Background;
addChild(bg);
char = new Character();
addChild(char);
char.x = stage.stageWidth/2;
char.y = 488;
b = new Bubbles();
addChild(b);
b2 = new Bubbles();
addChild(b2);
b2.y = +b2.height;
s = new Seaweed();
addChild(s);
pu = new PowerUp();
addChild(pu);
pu.x = 200;
pu.y = 450;
pu.height = 50;
pu.scaleX = pu.scaleY;
pu.gotoAndStop("SPIN");
hit = new hit1;
addChild(hit);
hit.x = char.x
hit.y = char.y - 50
end = new EndGame();
end.x = stage.stageWidth/2;
end.y = stage.stageHeight/2;
stage.addEventListener(Event.ENTER_FRAME, onFrame);
stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
stage.addEventListener(KeyboardEvent.KEY_UP, keyReleased);
}//main()
public function onFrame(e:Event)
{
if (!comp)
//Bubble Movement
b.y -= 1;
b2.y -= 1;
if (b.y >= stage.stageHeight)
{
b.y = b2.y + bg.height;
}
else if (b2.y >= stage.stageHeight)
{
b2.y = b.y + b2.height;
}
//Background & Character Movement
if (pressingRight && char.x < stage.stageWidth/2)
{
char.x += speed * 0.4
}
else if (pressingRight == true && (bg.width + bg.x) > stage.stageWidth)
{
bg.x -= speed * 0.4;
s.x -= speed * 0.6;
pu.x -= speed * 0.4;
}
else if (pressingRight == true)
{
char.x += speed * 0.4;
}
if (pressingLeft == true && char.x > stage.stageWidth/2)
{
char.x -= speed * 0.4;
}
else if (pressingLeft == true && bg.x <0)
{
bg.x += speed * 0.4;
s.x += speed * 0.6;
pu.x += speed * 0.4;
}
else if (pressingLeft)
{
char.x -= speed * 0.4;
}
//Boundaries
if (char.x > stage.stageWidth)
{
char.x = stage.stageWidth;
}
else if (char.x < 0)
{
char.x = 0;
}
//Character Looking Directions
if (pressingLeft == true)
{
char.scaleX = -1;
hit.x = char.x
}
if (pressingRight == true)
{
char.scaleX = 1;
hit.x = char.x
}
//Character Movements
if (pressingRight || pressingLeft)
{
char.gotoAndStop("WALK");
}
else if (!pressingRight || !pressingLeft)
{
char.gotoAndStop("IDLE");
}
//Getting the Power up
if (pu.hitTestObject(hit))
{
char.gotoAndStop("POWER");
comp = true;
pu.gotoAndStop("GONE");
}
// !end
else if (comp) //if completion is true
{
var animation = char.getChildAt(2); //
if (animation.currentFrame == animation.totalFrames)
{
animation.stop();
addChild(end);
}
}//Comp
}//onFrame
public function keyPressed(k:KeyboardEvent)
{
if (k.keyCode == Keyboard.RIGHT)
{
pressingRight = true;
}
else if (k.keyCode == Keyboard.LEFT)
{
pressingLeft = true;
}
} // keyPressed()
public function keyReleased(k:KeyboardEvent)
{
if (k.keyCode == Keyboard.RIGHT)
{
pressingRight = false;
}
else if (k.keyCode == Keyboard.LEFT)
{
pressingLeft = false;
}
} // keyReleased()
}//public class()
}//package()

Answer 1

If you're using a language with zero-based indexing (where array indexes start at 0, not 1) Then this could be the problem.
Frame 1 would be at index [0] and frame 2 would be at index [1].
If you have 2 frames for example and try to access the frame at index[2] you are stepping beyond the bounds of your array and this is probably why you are getting that error message.