#vulnerable code 
                             public Config load(String file) {
		Dom dom = new DefaultDom();
		// 获得Xml文档对象
		Document doc = dom.getDocument(file == null ? DEFAULT_CONFIG_FILE : file);
		// 得到根节点
		Element root = dom.getRoot(doc);
		load(root, dom);
		return config;
	} 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public Config load(String file) {
        Dom dom = new DefaultDom();
        Document doc = dom.getDocument(file == null ? DEFAULT_CONFIG_FILE : file);
        Element root = dom.getRoot(doc);
        load(root, dom);
        return config;
    }