Attach (recommended) or Link to PDF file here:
http://mariovalle.name/SciViz/1-s2.0-S0097849310001846-main.pdf

Configuration:
- Web browser and its version: Using pdf.js from Node.js through npm package `pdfjs-dist`
- Operating system and its version: Windows 10 64bits
- PDF.js version: 2.6.347
- Is a browser extension: No

Steps to reproduce the problem:
1. Load the file in acrobat
2. In document properties look at the Author field: it is `Samuel Silva; Beatriz Sousa Santos; Joaquim Madeira`
3. Look at  Additional metadata > advanced > dc:creator. It is marked as `seq container` and contains the 3 authors.
4. Using the code below gives: `"Author": "Samuel Silva"` that is, only the first one. And `"dc:creator": "Samuel SilvaBeatriz Sousa SantosJoaquim Madeira"`, that is the three authors squashed together without separators.

What is the expected behavior? (add screenshot)
In both fields the three authors as a single string with some sort of separator between them. Note that other pdf files that contains multiple authors already have them as a single string with names separated by commas.

The code used:
```
var pdfjsLib = require("pdfjs-dist/es5/build/pdf.js");
var pdfPath = "http://mariovalle.name/SciViz/1-s2.0-S0097849310001846-main.pdf";
var loadingTask = pdfjsLib.getDocument(pdfPath);
loadingTask.promise
  .then(function (doc) {
    var lastPromise;
    lastPromise = doc.getMetadata().then(function (data) {
      console.log(JSON.stringify(data.info, null, 2));
      if (data.metadata) {
        console.log(JSON.stringify(data.metadata.getAll(), null, 2));
      }
    });
  });
```
const name = entry.nodeName;
    if (name !== "rdf:bag" && name !== "rdf:seq" && name !== "rdf:alt") {
      return null;
    }
    return entry.childNodes.filter(node => node.nodeName === "rdf:li");
  }
  _getCreators(entry) {
    if (entry.nodeName !== "dc:creator") {
      return false;
    }
    if (!entry.hasChildNodes()) {
      return true;
    }
    
    const seqNode = entry.childNodes[0];
    const authors = this._getSequence(seqNode) || [];
    this._metadataMap.set(
      entry.nodeName,
      authors.map(node => node.textContent.trim())
    );
    return true;
  }
  _parse(xmlDocument) {