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 )

applyBoundingBox(tmpCtx, this._bbox);
    let grad;
    if (this._type === "axial") {
      grad = tmpCtx.createLinearGradient(
        this._p0[0],
        this._p0[1],
        this._p1[0],
        this._p1[1]
      );
    } else if (this._type === "radial") {
      grad = tmpCtx.createRadialGradient(
        this._p0[0],
        this._p0[1],
        this._r0,
        this._p1[0],
        this._p1[1],
        this._r1
      );
    }
    for (const colorStop of this._colorStops) {
      grad.addColorStop(colorStop[0], colorStop[1]);
    }
    tmpCtx.fillStyle = grad;
    tmpCtx.fill();
    const pattern = ctx.createPattern(tmpCanvas.canvas, "repeat");
    pattern.setTransform(createMatrix(ctx.mozCurrentTransformInverse));
    return pattern;
  }
}
function drawTriangle(data, context, p1, p2, p3, c1, c2, c3) {