Null object error; cannot access it - AS3 - actionscript-3

Question

I'm making a platform game. Im trying just to get the player to move around on the stage, and to be able to jump, with some type of gravity added to it. However, when I run it, I get this error: Error #1009: Cannot access a property or method of a null object reference.
package {
import flash.display.MovieClip;
import flash.events.MouseEvent;
import flash.events.KeyboardEvent;
import flash.events.Event;
import flash.ui.Keyboard;
public class Code1 extends MovieClip {
var charSpeed:int = 0;
var velocity:int = 0;
var gravity:Number = 1;
var Jump:Boolean = false;
var leftKey:Boolean;
var rightKey:Boolean;
var upKey:Boolean;
private var platform:Platform;
public function startGame(){
stage.addEventListener(KeyboardEvent.KEY_DOWN, checkKeyDown);
stage.addEventListener(KeyboardEvent.KEY_UP, checkKeyUp);
stage.addEventListener(Event.ENTER_FRAME, loop);
stage.addEventListener(Event.ENTER_FRAME, update);
}
public function Code() {
}
public function update(evt:Event){
moveChar();
}
public function moveChar(){
if (leftKey == true){
charSpeed -= 10;
}
if (rightKey == true){
charSpeed += 10;
}
if (upKey == true){
if(!Jump){
velocity -= 14;
Jump = true;
}
}
}
function checkKeyDown(evt:KeyboardEvent){
if (evt.keyCode == Keyboard.UP){
upKey = true;
}
else if (evt.keyCode == Keyboard.RIGHT){
rightKey = true;
}
else if (evt.keyCode == Keyboard.LEFT){
leftKey = true;
}
}
function checkKeyUp(evt:KeyboardEvent){
if (evt.keyCode == Keyboard.UP){
upKey = false;
}
else if (evt.keyCode == Keyboard.RIGHT){
rightKey = false;
}
else if (evt.keyCode == Keyboard.LEFT){
leftKey = false;
}
}
function loop(evt:Event){
player.x = charSpeed;
if (player.x < 0){
player.x = 0;
}
if (player.x > 550){
player.x = 550;
}
velocity += gravity;
if (!platform.hitTestPoint(player.x, player.y, true)){
player.y += velocity;
}
for (var i = 0; i < 10; i++){
if (platform.hitTestPoint(player.x, player.y, true)){
player.y--;
velocity = 0;
Jump = false;
}
}
}
}
}
My platform linkage is "Platform", but i set up a variable for it (or tried to). I debugged the code, and it came up with this line: player.x = charSpeed;
I have no idea what to do, if someone could help, that would be great.

Answer 1

You never declare or instantiate (ie player = new Player()) your player.
Alternatively, if your player is on the stage of your .fla timeline, it will need the instance name 'player'. That can be set in the object properties.

Answer 2

You player object is null.
I don't see the istantiation line as:
var player:Player = new Player();
Add it before use a property of your player