Attach (recommended) or Link to PDF file here:
[chinese.pdf](https://github.com/mozilla/pdf.js/files/6404389/download.1.pdf)

Configuration:
- Web browser and its version:90.0.4430.93
- Operating system and its version: mac 10.15.5
- PDF.js version: 2.9.146
- Is a browser extension:no

Steps to reproduce the problem:
1. The Chinese in the attachment cannot be rendered

Brower ✅
![image](https://user-images.githubusercontent.com/13477114/116678074-81782a00-a9db-11eb-8719-74f48fcebc2b.png)

PDF.js ❌ [https://mozilla.github.io/pdf.js/web/viewer.html](https://mozilla.github.io/pdf.js/web/viewer.html)
![image](https://user-images.githubusercontent.com/13477114/116678212-a371ac80-a9db-11eb-847f-dd1ad7752c13.png)


What is the expected behavior? (add screenshot)
**The Chinese character can be rendered**
What went wrong? (add screenshot)
**All of the Chinese character cannot be rendered**
Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

(baseEncoding.length || this.differences.length)
      ) {
        for (let i = 0; i < 256; ++i) {
          if (!forcePostTable && charCodeToGlyphId[i] !== undefined) {
            continue;
          }
          const glyphName = this.differences[i] || baseEncoding[i];
          if (!glyphName) {
            continue;
          }
          const glyphId = properties.glyphNames.indexOf(glyphName);
          if (glyphId > 0 && hasGlyph(glyphId)) {
            charCodeToGlyphId[i] = glyphId;
          }
        }
      }
    }
    if (charCodeToGlyphId.length === 0) {
      
      charCodeToGlyphId[0] = 0;
    }
    
    
    
    
    let glyphZeroId = numGlyphsOut - 1;
    if (!dupFirstEntry) {
      glyphZeroId = 0;
    }