Attach (recommended) or Link to PDF file here:

Configuration:
- Web browser and its version: Chrome 90.0.4430.93
- Operating system and its version: macOs Big Sur 11.2.3
- PDF.js version: 2.7.570
- Is a browser extension: No

Steps to reproduce the problem:
1. Load the attached pdf in https://mozilla.github.io/pdf.js/web/viewer.html
2. Go to page 46. Dotted lines are missing in the graphics (see screenshot from acrobat reader)

What is the expected behavior? (add screenshot) See the screenshot
[Technical_Guide_UK.pdf](https://github.com/mozilla/pdf.js/files/6413001/Technical_Guide_UK.pdf)
![Screenshot 2021-05-03 at 07 46 09](https://user-images.githubusercontent.com/3785784/116844541-a343fd80-abe3-11eb-94c3-d03b3dfd6769.png)

paddedHeight,
      false
    );
    const tmpCtx = tmpCanvas.context;
    const data = tmpCtx.createImageData(width, height);
    if (backgroundColor) {
      const bytes = data.data;
      for (let i = 0, ii = bytes.length; i < ii; i += 4) {
        bytes[i] = backgroundColor[0];
        bytes[i + 1] = backgroundColor[1];
        bytes[i + 2] = backgroundColor[2];
        bytes[i + 3] = 255;
      }
    }
    for (let i = 0, ii = figures.length; i < ii; i++) {
      drawFigure(data, figures[i], context);
    }
    tmpCtx.putImageData(data, BORDER_SIZE, BORDER_SIZE);
    const canvas = tmpCanvas.canvas;
    return {
      canvas,
      offsetX: offsetX - BORDER_SIZE * scaleX,
      offsetY: offsetY - BORDER_SIZE * scaleY,
      scaleX,
      scaleY,
    };
  }
  return createMeshCanvas;
})();
ShadingIRs.Mesh = {