Attach (recommended) or Link to PDF file here:

Configuration:
- Web browser and its version: Chrome 63.0.3239.132 
- Operating system and its version: Windows 10
- PDF.js version: using your official demo project
- Is a browser extension: No

Steps to reproduce the problem:
1.  Just load attached pdf
2.

What is the expected behavior? (add screenshot)
[E-WG18_105147.pdf](https://github.com/mozilla/pdf.js/files/1634833/E-WG18_105147.pdf)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/29802177/34986271-3ca71a5c-fab7-11e7-95e8-1739dda3cd04.png)

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;
    }