Follow up with issue: https://github.com/mozilla/pdf.js/issues/14146
Merged pull req: https://github.com/mozilla/pdf.js/pull/14189

Attach (recommended) or Link to PDF file here:
https://bug1708641.bmoattachments.org/attachment.cgi?id=9219459

- This popup appears because JS is enabled;
- And because the pdf contains some unsupported features (e.g. XFA);

Configuration:
- Firefox Nightly & Chrome
- macOS Big Sur 11.6

Steps to reproduce the problem:
1. Run gulp server
2. Open attached pdf

What is the expected behavior? 
No popup on open

What went wrong?
![error](https://user-images.githubusercontent.com/76935202/139354112-707887a2-a6a1-43a9-a92e-45d57c48206a.jpg)



case "de":
        return "DEU";
      case "es":
        return "ESP";
      case "fr":
        return "FRA";
      case "it":
        return "ITA";
      case "ko":
        return "KOR";
      case "ja":
        return "JPN";
      case "nl":
        return "NLD";
      case "no":
        return "NOR";
      case "pt":
        if (sub === "br") {
          return "PTB";
        }
        return "ENU";
      case "fi":
        return "SUO";
      case "SV":
        return "SVE";
      default:
        return "ENU";
    }
  }
  get activeDocs() {