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):

ttContext.hintsValid = false;
                  return;
                }
                stack.length = newStackLength;
              } else if (
                funcId in ttContext.functionsDefined &&
                !functionsCalled.includes(funcId)
              ) {
                callstack.push({ data, i, stackTop: stack.length - 1 });
                functionsCalled.push(funcId);
                pc = ttContext.functionsDefined[funcId];
                if (!pc) {
                  warn("TT: CALL non-existent function");
                  ttContext.hintsValid = false;
                  return;
                }
                data = pc.data;
                i = pc.i;
              }
            }
          }
        } else if (op === 0x2c && !tooComplexToFollowFunctions) {
          
          if (inFDEF || inELSE) {
            warn("TT: nested FDEFs not allowed");
            tooComplexToFollowFunctions = true;
          }
          inFDEF = true;
          
          lastDeff = i;