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
constructor(data) {
    try {
      this.root = new XFAParser().parse(XFAFactory._createDocument(data));
      const binder = new Binder(this.root);
      this.form = binder.bind();
      this.dataHandler = new DataHandler(this.root, binder.getData());
      this.form[$globalData].template = this.form;
    } catch (e) {
      warn(`XFA - an error occurred during parsing and binding: ${e}`);
    }
  }
  isValid() {
    return this.root && this.form;
  }
  _createPages() {
    try {
      this.pages = this.form[$toHTML]();
      this.dims = this.pages.children.map(c => {
        const { width, height } = c.attributes.style;
        return [0, 0, parseInt(width), parseInt(height)];
      });
    } catch (e) {
      warn(`XFA - an error occurred during layout: ${e}`);
    }
  }
  getBoundingBox(pageIndex) {