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 maskCtx = maskCanvas.context;
        maskCtx.save();
        putBinaryImageMask(maskCtx, image);
        maskCtx.globalCompositeOperation = "source-in";
        maskCtx.fillStyle = isPatternFill
          ? fillColor.getPattern(maskCtx, this)
          : fillColor;
        maskCtx.fillRect(0, 0, width, height);
        maskCtx.restore();
        ctx.save();
        ctx.transform.apply(ctx, image.transform);
        ctx.scale(1, -1);
        ctx.drawImage(maskCanvas.canvas, 0, 0, width, height, 0, -1, 1, 1);
        ctx.restore();
      }
    }
    paintImageXObject(objId) {
      if (!this.contentVisible) {
        return;
      }
      const imgData = objId.startsWith("g_")
        ? this.commonObjs.get(objId)
        : this.objs.get(objId);
      if (!imgData) {
        warn("Dependent image isn't ready yet");
        return;
      }
      this.paintInlineImageXObject(imgData);
    }
    paintImageXObjectRepeat(objId, scaleX, scaleY, positions) {