#vulnerable code 
                                void outerHtml(StringBuilder accum) {
        String html = StringEscapeUtils.escapeHtml(getWholeText());
        if (parent() instanceof Element && !((Element) parent()).preserveWhitespace()) {
            html = normaliseWhitespace(html);
        }

        if (siblingIndex() == 0 && parentNode instanceof Element && ((Element) parentNode).tag().canContainBlock() && !isBlank())
            indent(accum);
        accum.append(html);
    } 
                            #location 7 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                void outerHtmlHead(StringBuilder accum, int depth) {
        String html = StringEscapeUtils.escapeHtml(getWholeText());
        if (parent() instanceof Element && !((Element) parent()).preserveWhitespace()) {
            html = normaliseWhitespace(html);
        }

        if (siblingIndex() == 0 && parentNode instanceof Element && ((Element) parentNode).tag().canContainBlock() && !isBlank())
            indent(accum, depth);
        accum.append(html);
    }