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 gen = ref.gen;
    let num = ref.num;
    if (xrefEntry.gen !== gen) {
      const msg = `Inconsistent generation in XRef: ${ref}`;
      
      if (this._generationFallback && xrefEntry.gen < gen) {
        warn(msg);
        return this.fetchUncompressed(
          Ref.get(num, xrefEntry.gen),
          xrefEntry,
          suppressEncryption
        );
      }
      throw new XRefEntryException(msg);
    }
    const stream = this.stream.makeSubStream(
      xrefEntry.offset + this.stream.start
    );
    const parser = new Parser({
      lexer: new Lexer(stream),
      xref: this,
      allowStreams: true,
    });
    const obj1 = parser.getObj();
    const obj2 = parser.getObj();
    const obj3 = parser.getObj();
    if (obj1 !== num || obj2 !== gen || !(obj3 instanceof Cmd)) {
      throw new XRefEntryException(`Bad (uncompressed) XRef entry: ${ref}`);
    }