HtmlBuilder constructor sets driver field to null and then calls setXmlnsPolicy() method on it which casues NullPointerException.

public HtmlBuilder(SimpleNodeFactory nodeFactory, XmlViolationPolicy xmlPolicy) {
        super();
        this.simpleNodeFactory = nodeFactory;
        this.treeBuilder = new XOMTreeBuilder(nodeFactory);
        this.driver = null;
        this.driver.setXmlnsPolicy(XmlViolationPolicy.ALTER_INFOSET);
        setXmlPolicy(xmlPolicy);
}