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
factors: SegoeuiBoldItalicFactors,
    baseWidths: LiberationSansBoldItalicWidths,
    lineHeight: SegoeuiBoldItalicLineHeight,
  };
  t["Helvetica-Regular"] = {
    name: "LiberationSans-Regular",
    factors: HelveticaRegularFactors,
    baseWidths: LiberationSansRegularWidths,
    lineHeight: HelveticaRegularLineHeight,
  };
  t["Helvetica-Bold"] = {
    name: "LiberationSans-Bold",
    factors: HelveticaBoldFactors,
    baseWidths: LiberationSansBoldWidths,
    lineHeight: HelveticaBoldLineHeight,
  };
  t["Helvetica-Italic"] = {
    name: "LiberationSans-Italic",
    factors: HelveticaItalicFactors,
    baseWidths: LiberationSansItalicWidths,
    lineHeight: HelveticaItalicLineHeight,
  };
  t["Helvetica-BoldItalic"] = {
    name: "LiberationSans-BoldItalic",
    factors: HelveticaBoldItalicFactors,
    baseWidths: LiberationSansBoldItalicWidths,
    lineHeight: HelveticaBoldItalicLineHeight,
  };
});
function getXfaFontName(name) {