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)
````
this.wordSpacing = 0;
      this.textHScale = 1;
      this.textRise = 0;
      
      this.fillColor = SVG_DEFAULTS.fillColor;
      this.strokeColor = "#000000";
      this.fillAlpha = 1;
      this.strokeAlpha = 1;
      this.lineWidth = 1;
      this.lineJoin = "";
      this.lineCap = "";
      this.miterLimit = 0;
      this.dashArray = [];
      this.dashPhase = 0;
      this.dependencies = [];
      
      this.activeClipUrl = null;
      this.clipGroup = null;
      this.maskId = "";
    }
    clone() {
      return Object.create(this);
    }
    setCurrentPoint(x, y) {
      this.x = x;
      this.y = y;
    }
  }
  
  function opListToTree(opList) {