Steps to reproduce (this PDF):
[page4.pdf](https://github.com/mozilla/pdf.js/files/5990272/page4.pdf)

````
npm install
node_modules/.bin/gulp dist-install
node examples/node/pdf2svg.js /tmp/page4.pdf
````

Error:
````
Error: Invalid SVG dimensions
    at unreachable (/tmp/pdf.js/build/dist/legacy/build/pdf.js:2086:9)
    at assert (/tmp/pdf.js/build/dist/legacy/build/pdf.js:2091:5)
    at DOMSVGFactory.create (/tmp/pdf.js/build/dist/legacy/build/pdf.js:640:24)
    at SVGGraphics._makeTilingPattern (/tmp/pdf.js/build/dist/legacy/build/pdf.js:24178:36)
    at SVGGraphics._makeColorN_Pattern (/tmp/pdf.js/build/dist/legacy/build/pdf.js:24127:23)
    at SVGGraphics.setFillColorN (/tmp/pdf.js/build/dist/legacy/build/pdf.js:24088:39)
    at SVGGraphics.executeOpTree (/tmp/pdf.js/build/dist/legacy/build/pdf.js:23634:22)
    at /tmp/pdf.js/build/dist/legacy/build/pdf.js:23508:18
    at process._tickCallback (internal/process/next_tick.js:68:7)
    at Function.Module.runMain (internal/modules/cjs/loader.js:834:11)
````
} else {
          
          
          
          
        }
        let charWidth;
        if (vertical) {
          charWidth = width * widthAdvanceScale - spacing * fontDirection;
        } else {
          charWidth = width * widthAdvanceScale + spacing * fontDirection;
        }
        x += charWidth;
      }
      current.tspan.setAttributeNS(
        null,
        "x",
        current.xcoords.map(pf).join(" ")
      );
      if (vertical) {
        current.tspan.setAttributeNS(
          null,
          "y",
          current.ycoords.map(pf).join(" ")
        );
      } else {
        current.tspan.setAttributeNS(null, "y", pf(-current.y));
      }
      if (vertical) {
        current.y -= x;