Attach (recommended) or Link to PDF file here: https://d15k2d11r6t6rl.cloudfront.net/public/users/Integrators/a0a42ab5-3cb9-4912-84b7-3c6e47330d5c/smart-pr-805/Consumentenfolder_A5_zonder_paskruizen%20_2.pdf (and the similar other files under "Informatiefolder" on https://news.pressmailings.com/hvdm/partnertoolkit)

Configuration:
- Web browser and its version: Firefox 84.0 (64 bits)
- Operating system and its version: Arch Linux
- PDF.js version: 2.7.262 (built-in) and 2.7.434 (development version at time of writing)
- Is a browser extension: no

Steps to reproduce the problem:
1. Open the linked PDF file linked above.
2. Notice that the first page is rendered completely broken. There are no warnings/errors in the console unfortunately, and it's not related to layers since the document does not contain any.

What is the expected behavior? (add screenshot)
![good](https://user-images.githubusercontent.com/1993262/103363234-e158d580-4aba-11eb-9eb7-fe0db9f0a193.png)

What went wrong? (add screenshot)
![broken](https://user-images.githubusercontent.com/1993262/103363239-e4ec5c80-4aba-11eb-9f7d-3edac62ece3c.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension): -
const groupCtx = this.ctx;
    this.groupLevel--;
    this.ctx = this.groupStack.pop();
    composeSMask(this.ctx, this.current.activeSMask, groupCtx);
    this.ctx.restore();
    this.ctx.save(); 
    copyCtxState(groupCtx, this.ctx);
    
    this.current.resumeSMaskCtx = groupCtx;
    
    
    const deltaTransform = Util.transform(
      this.current.activeSMask.startTransformInverse,
      groupCtx.mozCurrentTransform
    );
    this.ctx.transform.apply(this.ctx, deltaTransform);
    
    groupCtx.save();
    groupCtx.setTransform(1, 0, 0, 1, 0, 0);
    groupCtx.clearRect(0, 0, groupCtx.canvas.width, groupCtx.canvas.height);
    groupCtx.restore();
  }
  resumeSMaskGroup() {