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)

switch (transferMaps.length) {
        case 1:
          transferMapRed = transferMaps[0];
          transferMapGreen = transferMaps[0];
          transferMapBlue = transferMaps[0];
          transferMapGray = transferMaps[0];
          break;
        case 4:
          transferMapRed = transferMaps[0];
          transferMapGreen = transferMaps[1];
          transferMapBlue = transferMaps[2];
          transferMapGray = transferMaps[3];
          break;
      }
    }
    
    
    if (imgData.kind === ImageKind.GRAYSCALE_1BPP) {
      
      const srcLength = src.byteLength;
      const dest32 = new Uint32Array(dest.buffer, 0, dest.byteLength >> 2);
      const dest32DataLength = dest32.length;
      const fullSrcDiff = (width + 7) >> 3;
      let white = 0xffffffff;
      let black = IsLittleEndianCached.value ? 0xff000000 : 0x000000ff;
      if (transferMapGray) {
        if (transferMapGray[0] === 0xff && transferMapGray[0xff] === 0) {
          [white, black] = [black, white];
        }
      }