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):

}
        
        
        
        for (let last = kids.length - 1; last >= 0; last--) {
          nodesToVisit.push(kids[last]);
        }
      }
      capability.reject(new Error(`Page index ${pageIndex} not found.`));
    }
    next();
    return capability.promise;
  }
  getPageIndex(pageRef) {
    
    
    
    const xref = this.xref;
    function pagesBeforeRef(kidRef) {
      let total = 0,
        parentRef;
      return xref
        .fetchAsync(kidRef)
        .then(function (node) {
          if (
            isRefsEqual(kidRef, pageRef) &&
            !isDict(node, "Page") &&
            !(isDict(node) && !node.has("Type") && node.has("Contents"))
          ) {
            throw new FormatError(