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 hiddenGroups = [];
      for (const groupRef of contentGroupRefs) {
        if (parsedOrderRefs.has(groupRef)) {
          continue;
        }
        hiddenGroups.push(groupRef.toString());
      }
      if (hiddenGroups.length) {
        order.push({ name: null, order: hiddenGroups });
      }
      return order;
    }
    function parseNestedOrder(ref, nestedLevels) {
      if (++nestedLevels > MAX_NESTED_LEVELS) {
        warn("parseNestedOrder - reached MAX_NESTED_LEVELS.");
        return null;
      }
      const value = xref.fetchIfRef(ref);
      if (!Array.isArray(value)) {
        return null;
      }
      const nestedName = xref.fetchIfRef(value[0]);
      if (typeof nestedName !== "string") {
        return null;
      }
      const nestedOrder = parseOrder(value.slice(1), nestedLevels);
      if (!nestedOrder || !nestedOrder.length) {
        return null;
      }
      return { name: stringToPDFString(nestedName), order: nestedOrder };