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):

properties.fixedPitch = false;
    if (properties.builtInEncoding) {
      
      
      adjustToUnicode(properties, properties.builtInEncoding);
    }
    
    
    
    let glyphZeroId = 1;
    if (font instanceof CFFFont) {
      glyphZeroId = font.numGlyphs - 1;
    }
    const mapping = font.getGlyphMapping(properties);
    let newMapping = null;
    let newCharCodeToGlyphId = mapping;
    
    
    if (!properties.cssFontInfo) {
      newMapping = adjustMapping(
        mapping,
        font.hasGlyphId.bind(font),
        glyphZeroId
      );
      this.toFontChar = newMapping.toFontChar;
      newCharCodeToGlyphId = newMapping.charCodeToGlyphId;
    }
    const numGlyphs = font.numGlyphs;
    function getCharCodes(charCodeToGlyphId, glyphId) {