#vulnerable code 
                                void outerHtmlHead(StringBuilder accum, int depth) {
        if (isBlock() || (parent() != null && parent().tag().canContainBlock() && siblingIndex() == 0))
            indent(accum, depth);
        accum
                .append("<")
                .append(tagName())
                .append(attributes.html());

        if (childNodes.isEmpty() && tag.isEmpty())
            accum.append(" />");
        else
            accum.append(">");
    } 
                            #location 2 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                boolean preserveWhitespace() {
        return tag.preserveWhitespace() || parent() != null && parent().preserveWhitespace();
    }