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):

let collection = null;
    try {
      const obj = this._catDict.get("Collection");
      if (isDict(obj) && obj.size > 0) {
        collection = obj;
      }
    } catch (ex) {
      if (ex instanceof MissingDataException) {
        throw ex;
      }
      info("Cannot fetch Collection entry; assuming no collection is present.");
    }
    return shadow(this, "collection", collection);
  }
  get acroForm() {
    let acroForm = null;
    try {
      const obj = this._catDict.get("AcroForm");
      if (isDict(obj) && obj.size > 0) {
        acroForm = obj;
      }
    } catch (ex) {
      if (ex instanceof MissingDataException) {
        throw ex;
      }
      info("Cannot fetch AcroForm entry; assuming no forms are present.");
    }
    return shadow(this, "acroForm", acroForm);
  }
  get metadata() {