Attach (recommended) or Link to PDF file here:
[298865.pdf](https://github.com/mozilla/pdf.js/files/2753236/298865.pdf)


Configuration:
- Web browser and its version:chrome 71.0.3578.98
- Operating system and its version:mac os 10.12.6
- PDF.js version:I use online demo in github
- Is a browser extension:no

Steps to reproduce the problem:
1. search "中华" or "电力" or so on,the highlight position is not right

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/10000986/51087378-7eff5100-178d-11e9-991a-005d77b82f31.png)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/10000986/51087374-6ee77180-178d-11e9-9707-281924f95fd0.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):
https://mozilla.github.io/pdf.js/web/viewer.html
expect(pageLabels).toEqual(null);
    });
    it("gets page labels", async function () {
      
      const loadingTask0 = getDocument(buildGetDocumentParams("bug793632.pdf"));
      const promise0 = loadingTask0.promise.then(function (pdfDoc) {
        return pdfDoc.getPageLabels();
      });
      
      const loadingTask1 = getDocument(buildGetDocumentParams("issue1453.pdf"));
      const promise1 = loadingTask1.promise.then(function (pdfDoc) {
        return pdfDoc.getPageLabels();
      });
      
      const loadingTask2 = getDocument(buildGetDocumentParams("rotation.pdf"));
      const promise2 = loadingTask2.promise.then(function (pdfDoc) {
        return pdfDoc.getPageLabels();
      });
      
      const loadingTask3 = getDocument(
        buildGetDocumentParams("bad-PageLabels.pdf")
      );
      const promise3 = loadingTask3.promise.then(function (pdfDoc) {
        return pdfDoc.getPageLabels();
      });
      const pageLabels = await Promise.all([
        promise0,
        promise1,
        promise2,
        promise3,