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)



}
  addToolButton() {
    
  }
  alert(
    cMsg,
    nIcon = 0,
    nType = 0,
    cTitle = "PDF.js",
    oDoc = null,
    oCheckbox = null
  ) {
    if (typeof cMsg === "object") {
      nType = cMsg.nType;
      cMsg = cMsg.cMsg;
    }
    cMsg = (cMsg || "").toString();
    nType =
      typeof nType !== "number" || isNaN(nType) || nType < 0 || nType > 3
        ? 0
        : nType;
    if (nType >= 2) {
      return this._externalCall("confirm", [cMsg]) ? 4 : 3;
    }
    this._externalCall("alert", [cMsg]);
    return 1;
  }
  beep() {