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
const stream = this.stream;
    stream.reset();
    if (!find(stream, PDF_HEADER_SIGNATURE)) {
      
      
      return;
    }
    stream.moveStart();
    
    const MAX_PDF_VERSION_LENGTH = 12;
    let version = "",
      ch;
    while ((ch = stream.getByte()) >  0x20) {
      if (version.length >= MAX_PDF_VERSION_LENGTH) {
        break;
      }
      version += String.fromCharCode(ch);
    }
    if (!this._version) {
      
      this._version = version.substring(5);
    }
  }
  parseStartXRef() {