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)

const figure = mesh.figures[index];
    assert(figure.type === "patch", "Unexpected patch mesh figure");
    const coords = mesh.coords,
      colors = mesh.colors;
    const pi = figure.coords;
    const ci = figure.colors;
    const figureMinX = Math.min(
      coords[pi[0]][0],
      coords[pi[3]][0],
      coords[pi[12]][0],
      coords[pi[15]][0]
    );
    const figureMinY = Math.min(
      coords[pi[0]][1],
      coords[pi[3]][1],
      coords[pi[12]][1],
      coords[pi[15]][1]
    );
    const figureMaxX = Math.max(
      coords[pi[0]][0],
      coords[pi[3]][0],
      coords[pi[12]][0],
      coords[pi[15]][0]
    );
    const figureMaxY = Math.max(
      coords[pi[0]][1],
      coords[pi[3]][1],
      coords[pi[12]][1],
      coords[pi[15]][1]