Attach (recommended) or Link to PDF file here:
http://help.adobe.com/en_US/livecycle/11.0/SampleForms/941/Form.pdf

- Web browser and its version: Firefox 89.0.1
- Operating system and its version: Windows 10 10.0.19043.1052
- PDF.js version: commit bdfcdd6f8326f22c135edfa29a341ea4c558f3d1
- Is a browser extension: No

Steps to reproduce the problem:
1. Enable XFA support
2. Open form

What is the expected behavior? (add screenshot)
Page 3 (of 4) renders
![image](https://user-images.githubusercontent.com/7104454/122686842-622e9980-d1e1-11eb-92ab-86fe488560f2.png)

What went wrong? (add screenshot)
Only 3 pages total render in pdf.js
this.form[$globalData].fontFinder.add(fonts);
  }
  getPages() {
    if (!this.pages) {
      this._createPages();
    }
    const pages = this.pages;
    this.pages = null;
    return pages;
  }
  serializeData(storage) {
    return this.dataHandler.serialize(storage);
  }
  static _createDocument(data) {
    if (!data["/xdp:xdp"]) {
      return data["xdp:xdp"];
    }
    return Object.values(data).join("");
  }
}
export { XFAFactory };