Attach (recommended) or Link to PDF file here:  [test.pdf](https://akmer.aikucun.com/a94a8fe5ccb19ba61c4c0873d391e987982fbbd3_1616477914120_83.pdf)


Configuration:
- Web browser and its version: chrome 87.0.4280.88
- Operating system and its version: windows10
- PDF.js version: 2.6.347
- Is a browser extension:

Steps to reproduce the problem:
1. just open 

What is the expected behavior? (add screenshot)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/17724610/112087066-473f8f80-8bc8-11eb-8efb-56139ec42a9c.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

const obj = this._catDict.getRaw("PageLabels");
    if (!obj) {
      return null;
    }
    const pageLabels = new Array(this.numPages);
    let style = null,
      prefix = "";
    const numberTree = new NumberTree(obj, this.xref);
    const nums = numberTree.getAll();
    let currentLabel = "",
      currentIndex = 1;
    for (let i = 0, ii = this.numPages; i < ii; i++) {
      if (i in nums) {
        const labelDict = nums[i];
        if (!isDict(labelDict)) {
          throw new FormatError("PageLabel is not a dictionary.");
        }
        if (
          labelDict.has("Type") &&
          !isName(labelDict.get("Type"), "PageLabel")
        ) {
          throw new FormatError("Invalid type in PageLabel dictionary.");
        }
        if (labelDict.has("S")) {
          const s = labelDict.get("S");
          if (!isName(s)) {
            throw new FormatError("Invalid style in PageLabel dictionary.");
          }
          style = s.name;