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)
````
gradient.setAttributeNS(null, "r", circleRadius);
              gradient.setAttributeNS(null, "fx", focalPoint[0]);
              gradient.setAttributeNS(null, "fy", focalPoint[1]);
              gradient.setAttributeNS(null, "fr", focalRadius);
              break;
            default:
              throw new Error(`Unknown RadialAxial type: ${args[1]}`);
          }
          for (const colorStop of colorStops) {
            const stop = this.svgFactory.createElement("svg:stop");
            stop.setAttributeNS(null, "offset", colorStop[0]);
            stop.setAttributeNS(null, "stop-color", colorStop[1]);
            gradient.appendChild(stop);
          }
          this.defs.appendChild(gradient);
          return `url(#${shadingId})`;
        case "Mesh":
          warn("Unimplemented pattern Mesh");
          return null;
        case "Dummy":
          return "hotpink";
        default:
          throw new Error(`Unknown IR type: ${args[0]}`);
      }
    }
    setDash(dashArray, dashPhase) {
      this.current.dashArray = dashArray;
      this.current.dashPhase = dashPhase;
    }
    constructPath(ops, args) {