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 )

scaleX = drawnWidth / MAX_GROUP_SIZE;
        drawnWidth = MAX_GROUP_SIZE;
      }
      if (drawnHeight > MAX_GROUP_SIZE) {
        scaleY = drawnHeight / MAX_GROUP_SIZE;
        drawnHeight = MAX_GROUP_SIZE;
      }
      let cacheId = "groupAt" + this.groupLevel;
      if (group.smask) {
        
        cacheId += "_smask_" + (this.smaskCounter++ % 2);
      }
      const scratchCanvas = this.cachedCanvases.getCanvas(
        cacheId,
        drawnWidth,
        drawnHeight,
        true
      );
      const groupCtx = scratchCanvas.context;
      
      
      groupCtx.scale(1 / scaleX, 1 / scaleY);
      groupCtx.translate(-offsetX, -offsetY);
      groupCtx.transform.apply(groupCtx, currentTransform);
      if (group.smask) {
        
        this.smaskStack.push({
          canvas: scratchCanvas.canvas,
          context: groupCtx,
          offsetX,