Attach (recommended) or Link to PDF file here:  [test.pdf](https://akmer.aikucun.com/a94a8fe5ccb19ba61c4c0873d391e987982fbbd3_1616477914120_83.pdf)


Configuration:
- Web browser and its version: chrome 87.0.4280.88
- Operating system and its version: windows10
- PDF.js version: 2.6.347
- Is a browser extension:

Steps to reproduce the problem:
1. just open 

What is the expected behavior? (add screenshot)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/17724610/112087066-473f8f80-8bc8-11eb-8efb-56139ec42a9c.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

const obj = this._catDict.get("Names");
    let attachments = null;
    if (obj && obj.has("EmbeddedFiles")) {
      const nameTree = new NameTree(obj.getRaw("EmbeddedFiles"), this.xref);
      const names = nameTree.getAll();
      for (const name in names) {
        const fs = new FileSpec(names[name], this.xref);
        if (!attachments) {
          attachments = Object.create(null);
        }
        attachments[stringToPDFString(name)] = fs.serializable;
      }
    }
    return shadow(this, "attachments", attachments);
  }
  _collectJavaScript() {
    const obj = this._catDict.get("Names");
    let javaScript = null;
    function appendIfJavaScriptDict(name, jsDict) {
      const type = jsDict.get("S");
      if (!isName(type, "JavaScript")) {
        return;
      }
      let js = jsDict.get("JS");