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)



/* Copyright 2020 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import { Color } from "./color.js";
import { EventDispatcher } from "./event.js";
import { FullScreen } from "./fullscreen.js";
import { PDFObject } from "./pdf_object.js";
import { Thermometer } from "./thermometer.js";
const VIEWER_TYPE = "PDF.js";
const VIEWER_VARIATION = "Full";
const VIEWER_VERSION = "10.0";
const FORMS_VERSION = undefined;
class App extends PDFObject {