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
}
        throw new FormatError(
          `TrueType Collection does not contain "${fontName}" font.`
        );
      }
      /**
       * Read the appropriate subtable from the cmap according to 9.6.6.4 from
       * PDF spec
       */
      function readCmapTable(cmap, file, isSymbolicFont, hasEncoding) {
        if (!cmap) {
          warn("No cmap table available.");
          return {
            platformId: -1,
            encodingId: -1,
            mappings: [],
            hasShortCmap: false,
          };
        }
        var segment;
        var start = (file.start ? file.start : 0) + cmap.offset;
        file.pos = start;
        file.skip(2); 
        var numTables = file.getUint16();
        var potentialTable;
        var canBreak = false;