Attach (recommended) or Link to PDF file here:
[test.pdf](https://github.com/mozilla/pdf.js/files/6270827/test.pdf)
Configuration:
- Web browser and its version:chrome 89
- Operating system and its version:win10
- PDF.js version: 2.4/2.7/2.8 no working
- Is a browser extension: no 

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/18545199/113852392-1ae26080-97cf-11eb-9dc9-0cecf52d267b.png)

What went wrong? (add screenshot)
![1617791294(1)](https://user-images.githubusercontent.com/18545199/113852355-10c06200-97cf-11eb-8672-598750f1093a.jpg)


console this log : **FormatError: TrueType Collection does not contain "DCWGQU+CambriaMath" font** 

any solution?thanks
segment = segments[segIndex];
            start = segment.start;
            var end = segment.end;
            var delta = segment.delta;
            offsetIndex = segment.offsetIndex;
            for (j = start; j <= end; j++) {
              if (j === 0xffff) {
                continue;
              }
              glyphId = offsetIndex < 0 ? j : offsets[offsetIndex + j - start];
              glyphId = (glyphId + delta) & 0xffff;
              mappings.push({
                charCode: j,
                glyphId,
              });
            }
          }
        } else if (format === 6) {
          
          
          
          
          
          var firstCode = file.getUint16();
          var entryCount = file.getUint16();
          for (j = 0; j < entryCount; j++) {
            glyphId = file.getUint16();
            var charCode = firstCode + j;
            mappings.push({
              charCode,