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):

throw new FormatError("Kid must be a reference.");
            }
            if (isRefsEqual(kid, kidRef)) {
              found = true;
              break;
            }
            kidPromises.push(
              xref.fetchAsync(kid).then(function (obj) {
                if (!isDict(obj)) {
                  throw new FormatError("Kid node must be a dictionary.");
                }
                if (obj.has("Count")) {
                  total += obj.get("Count");
                } else {
                  
                  total++;
                }
              })
            );
          }
          if (!found) {
            throw new FormatError("Kid reference not found in parent's kids.");
          }
          return Promise.all(kidPromises).then(function () {
            return [total, parentRef];
          });
        });
    }
    let total = 0;
    function next(ref) {