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):

if (!root || !isDict(root)) {
      return;
    }
    this.xref = xref;
    this.root = root;
    if (root.has("FS")) {
      this.fs = root.get("FS");
    }
    this.description = root.has("Desc")
      ? stringToPDFString(root.get("Desc"))
      : "";
    if (root.has("RF")) {
      warn("Related file specifications are not supported");
    }
    this.contentAvailable = true;
    if (!root.has("EF")) {
      this.contentAvailable = false;
      warn("Non-embedded file specifications are not supported");
    }
  }
  function pickPlatformItem(dict) {