Attach (recommended) or Link to PDF file here:
[example.pdf](https://github.com/mozilla/pdf.js/files/6916129/example.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: all
- PDF.js version: various versions, including 2.11.54
- Is a browser extension: no

Screenshot with visible textLayer:
![Screenshot from 2021-08-02 13-05-03](https://user-images.githubusercontent.com/6362989/127844878-f85e291f-2060-4028-be09-7835f32ccfaa.png)

Which means some letters at the beginning/end of text selection are missing when copying text.

info(
          "Attempting to fix invalid indexToLocFormat in head table: " +
            indexToLocFormat
        );
        
        
        
        
        
        
        
        
        
        const numGlyphsPlusOne = numGlyphs + 1;
        if (locaLength === numGlyphsPlusOne << 1) {
          
          data[50] = 0;
          data[51] = 0;
        } else if (locaLength === numGlyphsPlusOne << 2) {
          
          data[50] = 0;
          data[51] = 1;
        } else {
          throw new FormatError(
            "Could not fix indexToLocFormat: " + indexToLocFormat
          );
        }
      }
    }
    function sanitizeGlyphLocations(