Attach (recommended) or Link to PDF file here:

Configuration:
- Web browser and its version: Chrome 90.0.4430.93
- Operating system and its version: macOs Big Sur 11.2.3
- PDF.js version: 2.7.570
- Is a browser extension: No

Steps to reproduce the problem:
1. Load the attached pdf in https://mozilla.github.io/pdf.js/web/viewer.html
2. Go to page 46. Dotted lines are missing in the graphics (see screenshot from acrobat reader)

What is the expected behavior? (add screenshot) See the screenshot
[Technical_Guide_UK.pdf](https://github.com/mozilla/pdf.js/files/6413001/Technical_Guide_UK.pdf)
![Screenshot 2021-05-03 at 07 46 09](https://user-images.githubusercontent.com/3785784/116844541-a343fd80-abe3-11eb-94c3-d03b3dfd6769.png)

const cs = ColorSpace.parse({
      cs: dict.getRaw("ColorSpace") || dict.getRaw("CS"),
      xref,
      resources,
      pdfFunctionFactory,
      localColorSpaceCache,
    });
    this.cs = cs;
    this.background = dict.has("Background")
      ? cs.getRgb(dict.get("Background"), 0)
      : null;
    const fnObj = dict.getRaw("Function");
    const fn = fnObj ? pdfFunctionFactory.createFromArray(fnObj) : null;
    this.coords = [];
    this.colors = [];
    this.figures = [];
    const decodeContext = {
      bitsPerCoordinate: dict.get("BitsPerCoordinate"),
      bitsPerComponent: dict.get("BitsPerComponent"),
      bitsPerFlag: dict.get("BitsPerFlag"),
      decode: dict.getArray("Decode"),
      colorFn: fn,
      colorSpace: cs,
      numComps: fn ? 1 : cs.numComps,
    };
    const reader = new MeshStreamReader(stream, decodeContext);
    let patchMesh = false;
    switch (this.shadingType) {
      case ShadingType.FREE_FORM_MESH:
        decodeType4Shading(this, reader);