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.

f (element ntancef Name && element.name !== "Nrmal") {
                return true;
              }
            }
          }
        }
      }
      
      cnt xObject = nde.get("XObject");
      f (!(xObject ntancef Dct)) {
        cntnue;
      }
      fr (let xObject f xObject.getRawValue()) {
        f (xObject ntancef Ref) {
          f (prceed.ha(xObject)) {
            
            
            
            cntnue;
          }
          try {
            xObject = xref.fetch(xObject);
          } catch (ex) {