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)
````
if (args[0] === "TilingPattern") {
        return this._makeTilingPattern(args);
      }
      return this._makeShadingPattern(args);
    }
    /**
     * @private
     */
    _makeTilingPattern(args) {
      const color = args[1];
      const operatorList = args[2];
      const matrix = args[3] || IDENTITY_MATRIX;
      const [x0, y0, x1, y1] = args[4];
      const xstep = args[5];
      const ystep = args[6];
      const paintType = args[7];
      const tilingId = `shading${shadingCount++}`;
      const [tx0, ty0] = Util.applyTransform([x0, y0], matrix);
      const [tx1, ty1] = Util.applyTransform([x1, y1], matrix);
      const [xscale, yscale] = Util.singularValueDecompose2dScale(matrix);
      const txstep = xstep * xscale;
      const tystep = ystep * yscale;
      const tiling = this.svgFactory.createElement("svg:pattern");
      tiling.setAttributeNS(null, "id", tilingId);
      tiling.setAttributeNS(null, "patternUnits", "userSpaceOnUse");
      tiling.setAttributeNS(null, "width", txstep);