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)
````
height & 0xff,
        bitDepth, 
        colorType, 
        0x00, 
        0x00, 
        0x00, 
      ]);
      const idat = deflateSync(literals);
      
      const pngLength =
        PNG_HEADER.length + CHUNK_WRAPPER_SIZE * 3 + ihdr.length + idat.length;
      const data = new Uint8Array(pngLength);
      let offset = 0;
      data.set(PNG_HEADER, offset);
      offset += PNG_HEADER.length;
      writePngChunk("IHDR", ihdr, data, offset);
      offset += CHUNK_WRAPPER_SIZE + ihdr.length;
      writePngChunk("IDATA", idat, data, offset);
      offset += CHUNK_WRAPPER_SIZE + idat.length;
      writePngChunk("IEND", new Uint8Array(0), data, offset);
      return createObjectURL(data, "image/png", forceDataSchema);
    }
    
    return function convertImgDataToPng(imgData, forceDataSchema, isMask) {
      const kind =
        imgData.kind === undefined ? ImageKind.GRAYSCALE_1BPP : imgData.kind;
      return encode(imgData, kind, forceDataSchema, isMask);
    };
  })();
  class SVGExtraState {