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):

}
          if (unicodeOrCharCode === undefined) {
            
            
            if (
              !properties.glyphNames &&
              properties.hasIncludedToUnicodeMap &&
              !(this.toUnicode instanceof IdentityToUnicodeMap)
            ) {
              const unicode = this.toUnicode.get(charCode);
              if (unicode) {
                unicodeOrCharCode = unicode.codePointAt(0);
              }
            }
            if (unicodeOrCharCode === undefined) {
              continue; 
            }
          }
          for (let i = 0; i < cmapMappingsLength; ++i) {
            if (cmapMappings[i].charCode !== unicodeOrCharCode) {
              continue;
            }
            charCodeToGlyphId[charCode] = cmapMappings[i].glyphId;
            break;
          }
        }
      } else if (cmapPlatformId === 0) {
        
        for (let i = 0; i < cmapMappingsLength; ++i) {
          charCodeToGlyphId[cmapMappings[i].charCode] = cmapMappings[i].glyphId;