I'm new to Processing, and while trying to test some of the examples on the processing website, I came across the Sequential animation code

 
int numFrames = 12;  // The number of frames in the animation
int frame = 0;
PImage[] images = new PImage[numFrames];
   
void setup()
{
 size(200, 200);
 frameRate(30);
 
 images[0]  = loadImage("PT_anim0000.gif");
 images[1]  = loadImage("PT_anim0001.gif");
 images[2]  = loadImage("PT_anim0002.gif");
 images[3]  = loadImage("PT_anim0003.gif");
 images[4]  = loadImage("PT_anim0004.gif");
 images[5]  = loadImage("PT_anim0005.gif");
 images[6]  = loadImage("PT_anim0006.gif");
 images[7]  = loadImage("PT_anim0007.gif");
 images[8]  = loadImage("PT_anim0008.gif");
 images[9]  = loadImage("PT_anim0009.gif");
 images[10] = loadImage("PT_anim0010.gif");
 images[11] = loadImage("PT_anim0011.gif");
 
 // If you don't want to load each image separately
 // and you know how many frames you have, you
 // can create the filenames as the program runs.
 // The nf() command does number formatting, which will
 // ensure that the number is (in this case) 4 digits.
 //for(int i=0; i<numFrames; i++) {
 //  String imageName = "PT_anim" + nf(i, 4) + ".gif";
 //  images[i] = loadImage(imageName);
 //}
}

void draw()
{
 frame = (frame+1) % numFrames;  // Use % to cycle through frames
image(images[frame], 50, 50);
}

Each time I copy and paste the code from the website to processing on my computer, I get an error saying Null Pointer Exception for the highlighted line.

Any ideas on how to correct this?

Thanks!