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
for (const [, pdfFont] of this.fonts.entries()) {
        if (
          pdfFont.regular.name &&
          pdfFont.regular.name
            .replace(pattern, "")
            .toLowerCase()
            .startsWith(name)
        ) {
          maybe.push(pdfFont);
        }
      }
    }
    if (maybe.length === 0) {
      name = name.replace(/psmt|mt/gi, "");
      for (const [family, pdfFont] of this.fonts.entries()) {
        if (family.replace(pattern, "").toLowerCase().startsWith(name)) {
          maybe.push(pdfFont);
        }
      }
    }
    if (maybe.length === 0) {
      for (const pdfFont of this.fonts.values()) {
        if (
          pdfFont.regular.name &&
          pdfFont.regular.name
            .replace(pattern, "")
            .toLowerCase()
            .startsWith(name)
        ) {
          maybe.push(pdfFont);