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):

const tag = file.getString(4);
      const checksum = file.getInt32() >>> 0;
      const offset = file.getInt32() >>> 0;
      const length = file.getInt32() >>> 0;
      
      const previousPosition = file.pos;
      file.pos = file.start ? file.start : 0;
      file.skip(offset);
      const data = file.getBytes(length);
      file.pos = previousPosition;
      if (tag === "head") {
        
        data[8] = data[9] = data[10] = data[11] = 0;
        data[17] |= 0x20; 
      }
      return {
        tag,
        checksum,
        length,
        offset,
        data,
      };
    }
    function readOpenTypeHeader(ttf) {