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
import { getLookupTableFactory } from "./core_utils.js";
import { normalizeFontName } from "./fonts_utils.js";
const getXFAFontMap = getLookupTableFactory(function (t) {
  t["MyriadPro-Regular"] = {
    name: "LiberationSans-Regular",
    factors: MyriadProRegularFactors,
    baseWidths: LiberationSansRegularWidths,
    lineHeight: MyriadProRegularLineHeight,
  };
  t["MyriadPro-Bold"] = {
    name: "LiberationSans-Bold",
    factors: MyriadProBoldFactors,
    baseWidths: LiberationSansBoldWidths,
    lineHeight: MyriadProBoldLineHeight,
  };
  t["MyriadPro-It"] = {
    name: "LiberationSans-Italic",
    factors: MyriadProItalicFactors,
    baseWidths: LiberationSansItalicWidths,
    lineHeight: MyriadProItalicLineHeight,
  };
  t["MyriadPro-BoldIt"] = {
    name: "LiberationSans-BoldItalic",
    factors: MyriadProBoldItalicFactors,
    baseWidths: LiberationSansBoldItalicWidths,
    lineHeight: MyriadProBoldItalicLineHeight,
  };
  t.ArialMT =
    t.Arial =
    t["Arial-Regular"] =