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.

mappings: [],
          hasShortCmap: false,
        };
      }
      let segment;
      let start = (file.start ? file.start : 0) + cmap.offset;
      file.pos = start;
      file.skip(2); 
      const numTables = file.getUint16();
      let potentialTable;
      let canBreak = false;
      
      
      
      
      
      
      for (let i = 0; i < numTables; i++) {
        const platformId = file.getUint16();
        const encodingId = file.getUint16();
        const offset = file.getInt32() >>> 0;
        let useTable = false;
        
        
        if (
          potentialTable &&
          potentialTable.platformId === platformId &&
          potentialTable.encodingId === encodingId
        ) {
          continue;