Trying to read a pdf file using PDFJS.getDocument function. The pdf worker is throwing


UnknownErrorException {
 name: "UnknownErrorException", 
 message: "Invalid root reference", 
 details: "FormatError: Invalid root reference"
}

The error can be easily reproduced calling PDFJS.getDocument(pdfUrl) using the attached pdf
[110229_10312017_6810306.pdf](https://github.com/mozilla/pdf.js/files/1444166/110229_10312017_6810306.pdf)


const tableOffset = xrefEntry.offset;
    const stream = this.fetch(Ref.get(tableOffset, 0));
    if (!(stream instanceof BaseStream)) {
      throw new FormatError("bad ObjStm stream");
    }
    const first = stream.dict.get("First");
    const n = stream.dict.get("N");
    if (!Number.isInteger(first) || !Number.isInteger(n)) {
      throw new FormatError("invalid first and n parameters for ObjStm stream");
    }
    let parser = new Parser({
      lexer: new Lexer(stream),
      xref: this,
      allowStreams: true,
    });
    const nums = new Array(n);