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 (!this.contentAvailable) {
        return null;
      }
      if (!this.contentRef && this.root) {
        this.contentRef = pickPlatformItem(this.root.get("EF"));
      }
      var content = null;
      if (this.contentRef) {
        var xref = this.xref;
        var fileObj = xref.fetchIfRef(this.contentRef);
        if (fileObj && isStream(fileObj)) {
          content = fileObj.getBytes();
        } else {
          warn(
            "Embedded file specification points to non-existing/invalid " +
              "content"
          );
        }
      } else {
        warn("Embedded file specification does not have a content");
      }
      return content;
    },
    get serializable() {