Attach (recommended) or Link to PDF file here:
[output.pdf](https://github.com/mozilla/pdf.js/files/6374987/output.pdf)

Configuration:
- Web browser and its version: Firefox 88.0
- Operating system and its version: macOS Big Sur 11.2.3 (20D91)
- PDF.js version: 2.8.243
- Is a browser extension: no/Firefox built-in

Steps to reproduce the problem:
1.  add Ink-Annotations to a pdf (i use https://github.com/highkite/pdfAnnotate, Annotations with appearance streams are shown correctly)
2. open output file in firefox

What is the expected behavior? 
The annotations should be visible.
![Bildschirmfoto 2021-04-26 um 09 15 48](https://user-images.githubusercontent.com/33630884/116043809-6a020f80-a670-11eb-973c-6f2df3dae532.png)

What went wrong? 
The annotations are added to the dom but invisible.
![Bildschirmfoto 2021-04-26 um 09 18 26](https://user-images.githubusercontent.com/33630884/116043867-7e460c80-a670-11eb-964d-0cc2c6dbfb61.png)

Tested successfull with FoxitReader, AcrobatReader, Chrome and Safari.
this.creationDate = isString(creationDate) ? creationDate : null;
  }
  _setDefaultAppearance({
    xref,
    extra,
    strokeColor,
    fillColor,
    blendMode,
    pointsCallback,
  }) {
    let minX = Number.MAX_VALUE;
    let minY = Number.MAX_VALUE;
    let maxX = Number.MIN_VALUE;
    let maxY = Number.MIN_VALUE;
    const buffer = ["q"];
    if (extra) {
      buffer.push(extra);
    }
    if (strokeColor) {
      buffer.push(`${strokeColor[0]} ${strokeColor[1]} ${strokeColor[2]} RG`);
    }
    if (fillColor) {
      buffer.push(`${fillColor[0]} ${fillColor[1]} ${fillColor[2]} rg`);