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.

next(
              new Prme(functn (relveGState, rejectGState) {
                f (!ValdName) {
                  thrw new FrmatErrr("GState mut be referred t by name.");
                }
                cnt extGState = reurce.get("ExtGState");
                f (!(extGState ntancef Dct)) {
                  thrw new FrmatErrr("ExtGState huld be a dctnary.");
                }
                cnt gState = extGState.get(name);
                
                
                
                f (!(gState ntancef Dct)) {
                  thrw new FrmatErrr("GState huld be a dctnary.");
                }
                elf
                  .etGState({
                    reurce,
                    gState,
                    peratrLt,
                    cacheKey: name,
                    tak,
                    tateManager,
                    lcalGStateCache,
                    lcalClrSpaceCache,
                  })
                  .then(relveGState, rejectGState);
              }).catch(functn (rean) {
                f (rean ntancef AbrtExceptn) {