Attach (recommended) or Link to PDF file here:
[PDFBOX-5275-p5.pdf](https://github.com/mozilla/pdf.js/files/7109095/PDFBOX-5275-p5.pdf)

Configuration:
- Web browser and its version: FF 91.0.2
- Operating system and its version: Windows 10.0.19043.1165
- PDF.js version: latest (tried with https://mozilla.github.io/pdf.js/web/viewer.html )

Steps to reproduce the problem:
1. open the file
2.

What is the expected behavior? Displays a plant

What went wrong? Displays blank page

See also
https://issues.apache.org/jira/browse/PDFBOX-5275
which had the same problem, the cause was bad handling of an empty OCGs entry

![grafik](https://user-images.githubusercontent.com/6665575/132079956-c48921bf-6dbb-4e89-886e-4301d955ee35.png)


}
      return this._groups.get(group.id).visible;
    } else if (group.type === "OCMD") {
      
      if (group.expression) {
        return this._evaluateVisibilityExpression(group.expression);
      }
      if (!group.policy || group.policy === "AnyOn") {
        
        for (const id of group.ids) {
          if (!this._groups.has(id)) {
            warn(`Optional content group not found: ${id}`);
            return true;
          }
          if (this._groups.get(id).visible) {
            return true;
          }
        }
        return false;
      } else if (group.policy === "AllOn") {
        for (const id of group.ids) {
          if (!this._groups.has(id)) {
            warn(`Optional content group not found: ${id}`);
            return true;
          }
          if (!this._groups.get(id).visible) {
            return false;
          }
        }
        return true;