NullPointerException on MainController

[xaviml]

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at controller.MainController.openImage(MainController.java:103)

@Override
public void openImage(String path) {
        Imatge img = disk.openImage(path);
        this.images.clear();
        this.imagesCopia.clear(); //NullPointerException in this line
        this.images.add(img);
        this.imagesCopia.add(img);
}

[Folch]

Done