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):

let config = null;
    try {
      const properties = this._catDict.get("OCProperties");
      if (!properties) {
        return shadow(this, "optionalContentConfig", null);
      }
      const defaultConfig = properties.get("D");
      if (!defaultConfig) {
        return shadow(this, "optionalContentConfig", null);
      }
      const groupsData = properties.get("OCGs");
      if (!Array.isArray(groupsData)) {
        return shadow(this, "optionalContentConfig", null);
      }
      const groups = [];
      const groupRefs = [];
      
      for (const groupRef of groupsData) {
        if (!isRef(groupRef)) {
          continue;
        }
        groupRefs.push(groupRef);
        const group = this.xref.fetchIfRef(groupRef);
        groups.push({
          id: groupRef.toString(),
          name: isString(group.get("Name"))
            ? stringToPDFString(group.get("Name"))
            : null,
          intent: isString(group.get("Intent"))