Attach (recommended) or Link to PDF file here:
[FormDB2_fr.pdf](https://github.com/mozilla/pdf.js/files/7352426/FormDB2_fr.pdf)

Configuration:
- Web browser and its version: Firefox nightly
- Operating system and its version: linux debian

Steps to reproduce the problem:
1. Open the pdf
2. The image on the top of each pages is missing 

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/5641725/137465500-e8788893-f33d-4532-871d-43b464fa85f4.png)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/5641725/137465363-f2b35fe4-6776-45e9-b9e4-ccef6d9ad670.png)

startColor = startColor ? startColor[$toStyle]() : "#FFFFFF";
    const endColor = this.color ? this.color[$toStyle]() : "#000000";
    const width = 5;
    const cmd = "repeating-linear-gradient";
    const colors = `${startColor},${startColor} ${width}px,${endColor} ${width}px,${endColor} ${
      2 * width
    }px`;
    switch (this.type) {
      case "crossHatch":
        return `${cmd}(to top,${colors}) ${cmd}(to right,${colors})`;
      case "crossDiagonal":
        return `${cmd}(45deg,${colors}) ${cmd}(-45deg,${colors})`;
      case "diagonalLeft":
        return `${cmd}(45deg,${colors})`;
      case "diagonalRight":
        return `${cmd}(-45deg,${colors})`;
      case "horizontal":
        return `${cmd}(to top,${colors})`;
      case "vertical":
        return `${cmd}(to right,${colors})`;
    }
    return "";
  }
}
class Picture extends StringObject {