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 )

while (this.stateStack.length || this.current.activeSMask !== null) {
        this.restore();
      }
      this.ctx.restore();
      if (this.transparentCanvas) {
        this.ctx = this.compositeCtx;
        this.ctx.save();
        this.ctx.setTransform(1, 0, 0, 1, 0, 0); 
        this.ctx.drawImage(this.transparentCanvas, 0, 0);
        this.ctx.restore();
        this.transparentCanvas = null;
      }
      this.cachedCanvases.clear();
      if (this.imageLayer) {
        this.imageLayer.endLayout();
      }
    }
    
    setLineWidth(width) {
      this.current.lineWidth = width;
      this.ctx.lineWidth = width;
    }
    setLineCap(style) {