#vulnerable code 
                                public void sortXml() {
        newDocument = (Document) originalDocument.clone();
        final Element rootElement = (Element) originalDocument.getRootElement().clone();

        HierarchyWrapper rootWrapper = factory.createFromRootElement(rootElement);

        rootWrapper.createWrappedStructure(factory);
        rootWrapper.detachStructure();
        rootWrapper.sortStructureAttributes();
        rootWrapper.sortStructureElements();
        rootWrapper.connectXmlStructure();

        newDocument.setRootElement(rootWrapper.getElementContent().getContent());
    } 
                            #location 13 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public void sortXml() {
        newDocument = (Document) originalDocument.clone();
        final Element rootElement = (Element) originalDocument.getRootElement().clone();

        HierarchyRootWrapper rootWrapper = factory.createFromRootElement(rootElement);

        rootWrapper.createWrappedStructure(factory);
        rootWrapper.detachStructure();
        rootWrapper.sortStructureAttributes();
        rootWrapper.sortStructureElements();
        rootWrapper.connectXmlStructure();

        newDocument.setRootElement(rootWrapper.getElementContent().getContent());
    }