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)

let i, ii, j, jj;
    const coords = mesh.coords;
    const coordsPacked = new Float32Array(coords.length * 2);
    for (i = 0, j = 0, ii = coords.length; i < ii; i++) {
      const xy = coords[i];
      coordsPacked[j++] = xy[0];
      coordsPacked[j++] = xy[1];
    }
    mesh.coords = coordsPacked;
    const colors = mesh.colors;
    const colorsPacked = new Uint8Array(colors.length * 3);
    for (i = 0, j = 0, ii = colors.length; i < ii; i++) {
      const c = colors[i];
      colorsPacked[j++] = c[0];
      colorsPacked[j++] = c[1];
      colorsPacked[j++] = c[2];
    }
    mesh.colors = colorsPacked;
    const figures = mesh.figures;
    for (i = 0, ii = figures.length; i < ii; i++) {
      const figure = figures[i],
        ps = figure.coords,
        cs = figure.colors;
      for (j = 0, jj = ps.length; j < jj; j++) {
        ps[j] *= 2;
        cs[j] *= 3;
      }
    }
  }
  function Mesh(