Attach (recommended) or Link to PDF file here:
[test.pdf](https://github.com/mozilla/pdf.js/files/6715502/test.pdf)

Configuration:
- Web browser and its version: Google Chrome Version 91.0.4472.114 
- Operating system and its version: Windows 10 Enterprise
- PDF.js version: 
- Is a browser extension: yes

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



What is the expected behavior? (add screenshot)
show symbol
![image](https://user-images.githubusercontent.com/50500976/123409847-55ca8800-d5b7-11eb-9e5b-c7f3b33c00e1.png)

What went wrong? (add screenshot)
Does not show symbol
![image](https://user-images.githubusercontent.com/50500976/123409707-274cad00-d5b7-11eb-9a64-b11dcf3cdc3f.png)
Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension): Latest Version Chrome extension

toUnicode[charCode] = String.fromCharCode(unicode);
    }
  }
  if (toUnicode.length > 0) {
    properties.toUnicode.amend(toUnicode);
  }
}
/**
 * NOTE: This function should only be called at the *end* of font-parsing,
 *       after e.g. `adjustToUnicode` has run, to prevent any issues.
 */
function amendFallbackToUnicode(properties) {
  if (!properties.fallbackToUnicode) {
    return;
  }
  if (properties.toUnicode instanceof IdentityToUnicodeMap) {
    return;
  }
  const toUnicode = [];
  for (const charCode in properties.fallbackToUnicode) {
    if (properties.toUnicode.has(charCode)) {
      continue; 
    }
    toUnicode[charCode] = properties.fallbackToUnicode[charCode];
  }
  if (toUnicode.length > 0) {
    properties.toUnicode.amend(toUnicode);
  }
}
class Glyph {