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
if (this.xfaData) {
      return this.xfaData.bbox;
    }
    const box = this._getInheritableProperty(name,  true);
    if (Array.isArray(box) && box.length === 4) {
      if (box[2] - box[0] !== 0 && box[3] - box[1] !== 0) {
        return box;
      }
      warn(`Empty /${name} entry.`);
    }
    return null;
  }
  get mediaBox() {
    
    return shadow(
      this,
      "mediaBox",
      this._getBoundingBox("MediaBox") || LETTER_SIZE_MEDIABOX
    );
  }
  get cropBox() {
    
    return shadow(
      this,
      "cropBox",
      this._getBoundingBox("CropBox") || this.mediaBox
    );
  }
  get userUnit() {