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
}
    if (!Array.isArray(xfa) || xfa.length === 0) {
      return null;
    }
    for (let i = 0, ii = xfa.length; i < ii; i += 2) {
      let name;
      if (i === 0) {
        name = "xdp:xdp";
      } else if (i === ii - 2) {
        name = "/xdp:xdp";
      } else {
        name = xfa[i];
      }
      if (!entries.hasOwnProperty(name)) {
        continue;
      }
      const data = this.xref.fetchIfRef(xfa[i + 1]);
      if (!isStream(data) || data.isEmpty) {
        continue;
      }
      try {
        entries[name] = stringToUTF8String(data.getString());
      } catch (_) {
        warn("XFA - Invalid utf-8 string.");
        return null;
      }
    }
    return entries;
  }
  get xfaFactory() {