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 )

context,
            ps[q + verticesPerRow + 1],
            ps[q + 1],
            ps[q + verticesPerRow],
            cs[q + verticesPerRow + 1],
            cs[q + 1],
            cs[q + verticesPerRow]
          );
        }
      }
      break;
    case "triangles":
      for (i = 0, ii = ps.length; i < ii; i += 3) {
        drawTriangle(
          data,
          context,
          ps[i],
          ps[i + 1],
          ps[i + 2],
          cs[i],
          cs[i + 1],
          cs[i + 2]
        );
      }
      break;
    default:
      throw new Error("illegal figure");
  }
}
class MeshShadingPattern extends BaseShadingPattern {