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 glyph = glyphs[i];
        if (isNum(glyph)) {
          x += (spacingDir * glyph * fontSize) / 1000;
          continue;
        }
        let restoreNeeded = false;
        const spacing = (glyph.isSpace ? wordSpacing : 0) + charSpacing;
        const character = glyph.fontChar;
        const accent = glyph.accent;
        let scaledX, scaledY;
        let width = glyph.width;
        if (vertical) {
          const vmetric = glyph.vmetric || defaultVMetrics;
          const vx =
            -(glyph.vmetric ? vmetric[1] : width * 0.5) * widthAdvanceScale;
          const vy = vmetric[2] * widthAdvanceScale;
          width = vmetric ? -vmetric[0] : width;
          scaledX = vx / fontSizeScale;
          scaledY = (x + vy) / fontSizeScale;
        } else {
          scaledX = x / fontSizeScale;
          scaledY = 0;
        }
        if (font.remeasure && width > 0) {
          
          
          
          const measuredWidth =
            ((ctx.measureText(character).width * 1000) / fontSize) *
            fontSizeScale;