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 )

const ps = figure.coords;
  const cs = figure.colors;
  let i, ii;
  switch (figure.type) {
    case "lattice":
      const verticesPerRow = figure.verticesPerRow;
      const rows = Math.floor(ps.length / verticesPerRow) - 1;
      const cols = verticesPerRow - 1;
      for (i = 0; i < rows; i++) {
        let q = i * verticesPerRow;
        for (let j = 0; j < cols; j++, q++) {
          drawTriangle(
            data,
            context,
            ps[q],
            ps[q + 1],
            ps[q + verticesPerRow],
            cs[q],
            cs[q + 1],
            cs[q + verticesPerRow]
          );
          drawTriangle(
            data,