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 hasFields = Array.isArray(fields) && fields.length > 0;
      formInfo.hasFields = hasFields; 
      
      
      const xfa = acroForm.get("XFA");
      formInfo.hasXfa =
        (Array.isArray(xfa) && xfa.length > 0) ||
        (isStream(xfa) && !xfa.isEmpty);
      
      
      
      
      
      
      
      const sigFlags = acroForm.get("SigFlags");
      const hasSignatures = !!(sigFlags & 0x1);
      const hasOnlyDocumentSignatures =
        hasSignatures && this._hasOnlyDocumentSignatures(fields);
      formInfo.hasAcroForm = hasFields && !hasOnlyDocumentSignatures;
      formInfo.hasSignatures = hasSignatures;
    } catch (ex) {
      if (ex instanceof MissingDataException) {
        throw ex;
      }
      warn(`Cannot fetch form information: "${ex}".`);
    }
    return shadow(this, "formInfo", formInfo);
  }
  get documentInfo() {