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)
````
for (const opTreeElement of opTree) {
        const fn = opTreeElement.fn;
        const fnId = opTreeElement.fnId;
        const args = opTreeElement.args;
        switch (fnId | 0) {
          case OPS.beginText:
            this.beginText();
            break;
          case OPS.dependency:
            
            break;
          case OPS.setLeading:
            this.setLeading(args);
            break;
          case OPS.setLeadingMoveText:
            this.setLeadingMoveText(args[0], args[1]);
            break;
          case OPS.setFont:
            this.setFont(args);
            break;
          case OPS.showText:
            this.showText(args[0]);
            break;
          case OPS.showSpacedText:
            this.showText(args[0]);
            break;