#vulnerable code 
                             void outerHtmlHead(Appendable accum, int depth, Document.OutputSettings out) throws IOException {
        if (out.prettyPrint() && ((siblingIndex() == 0 && parentNode instanceof Element && ((Element) parentNode).tag().formatAsBlock() && !isBlank()) || (out.outline() && siblingNodes().size()>0 && !isBlank()) ))
            indent(accum, depth, out);

        boolean normaliseWhite = out.prettyPrint() && !Element.preserveWhitespace(parent());
        Entities.escape(accum, coreValue(), out, false, normaliseWhite, false);
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             void outerHtmlHead(Appendable accum, int depth, Document.OutputSettings out) throws IOException {
        final boolean prettyPrint = out.prettyPrint();
        if (prettyPrint && ((siblingIndex() == 0 && parentNode instanceof Element && ((Element) parentNode).tag().formatAsBlock() && !isBlank()) || (out.outline() && siblingNodes().size()>0 && !isBlank()) ))
            indent(accum, depth, out);

        final boolean normaliseWhite = prettyPrint && !Element.preserveWhitespace(parentNode);
        final boolean stripWhite = prettyPrint && parentNode instanceof Document;
        Entities.escape(accum, coreValue(), out, false, normaliseWhite, stripWhite);
    }