Cannot get 'blur' like trail effect in "Interphase Example 5"

[Dandibot]

I'm trying to follow the Interphase book examples, and I'm stuck at the rendering stage (Example 5, page 76) with an 

Uncaught TypeError: Cannot read property 'drawImage' of null at MyGame.StateA.render (stateA.js:66)

The JS code (copy-paste from the book):

var MyGame = {};
 
MyGame.StateA = function (game) {
 
	this.b = 0;
	this.frames = [];
	this.start = false;
 
	this.sprite = null; 
};
 
 MyGame.StateA.prototype = {
 
     preload: function () {
 
         this.load.image('background', '../assets/wave.jpg');
         this.load.image('phaser', '../assets/phaser.png');
         this.load.image('asuna', '../assets/fairy_dance_asuna_by_vali233.png');
 
     },
 
     create: function () {
 
         //  Create 10 'frames'
         for (var i = 0; i < 10; i++)
         {
             this.frames.push(this.make.bitmapData(game.width, game.height));
         }
 
         this.add.sprite(0, 0, 'background');
 
         this.add.sprite(640, 553, 'phaser');
 
         this.add.text(16, 16, 
             "State Example: preRender", 
             { font: "16px Arial", fill: "#ffffff" });
 
       this.sprite = this.add.sprite(
           this.world.centerX, 
           this.world.centerY, 
           'asuna');
 
         this.sprite.anchor.set(0.5);
 
         this.add.tween(this.sprite.scale).to( 
             { x: 0.2, y: 0.2 }, 
             2000, 
             "Sine.easeInOut", true, 500, -1, true);  
    },

    update: function () {

        this.sprite.rotation += 0.01;
 
     },
 
     preRender: function () {
 
         this.frames[this.b].cls();
         this.frames[this.b].copyRect(
             this.game.canvas, 
             this.world.bounds, 
             0, 0, 0.1
         );
 
         this.b++;
 
         if (this.b === 10)
         {
             this.start = true;
             this.b = 0;
         }
 
     },
 
     render: function () {
 
         if (this.start)
         {
             //  The frame buffer is full, so lets start drawing them back
             for (var i = 0; i < 10; i++)
             {
                 this.game.context.drawImage(this.frames[i].canvas, 0, 0);
             }
         }
 
     }
 
 };

From what I can see, the frames start to render, but stop and throw this error. The "game.context" is null when I check in the console.

EDIT:

As usual I found the answer just after posting. I didn't define a context when I created a new Phaser.Game instance (in the HTML file). 

Problem solved (wish I could delete this post) :|

Edited March 22, 2017 by Dandibot
Found the solution just after posting