Attach (recommended) or Link to PDF file here:
[PATTYP2.pdf](https://github.com/mozilla/pdf.js/files/6471935/PATTYP2.pdf)

Configuration:
- Web browser and its version: FF 88.0.1
- Operating system and its version: W10.0.19042.985
- PDF.js version: https://mozilla.github.io/pdf.js/web/viewer.html

Steps to reproduce the problem:
1. open file to display

What is the expected behavior? (add screenshot)
![grafik](https://user-images.githubusercontent.com/6665575/118114800-5e407800-b3e8-11eb-860f-019f48a8eabf.png)

What went wrong? (add screenshot)
![grafik](https://user-images.githubusercontent.com/6665575/118114841-6c8e9400-b3e8-11eb-8252-1517e5d76475.png)

(memo for me: when fixed, check the files in https://issues.apache.org/jira/browse/PDFBOX-1958 )

c3 = tmp;
  }
  if (coords[p1 + 1] > coords[p2 + 1]) {
    tmp = p1;
    p1 = p2;
    p2 = tmp;
    tmp = c1;
    c1 = c2;
    c2 = tmp;
  }
  const x1 = (coords[p1] + context.offsetX) * context.scaleX;
  const y1 = (coords[p1 + 1] + context.offsetY) * context.scaleY;
  const x2 = (coords[p2] + context.offsetX) * context.scaleX;
  const y2 = (coords[p2 + 1] + context.offsetY) * context.scaleY;
  const x3 = (coords[p3] + context.offsetX) * context.scaleX;
  const y3 = (coords[p3 + 1] + context.offsetY) * context.scaleY;
  if (y1 >= y3) {
    return;
  }
  const c1r = colors[c1],
    c1g = colors[c1 + 1],
    c1b = colors[c1 + 2];
  const c2r = colors[c2],
    c2g = colors[c2 + 1],
    c2b = colors[c2 + 2];
  const c3r = colors[c3],
    c3g = colors[c3 + 1],
    c3b = colors[c3 + 2];
  const minY = Math.round(y1),
    maxY = Math.round(y3);