Crashes if it finds map

`map $aa $bb { }`

gives the error:
```
File "C:\Python27\lib\site-packages\nginx.py", line 515, in loadf
    return load(f)
  File "C:\Python27\lib\site-packages\nginx.py", line 505, in load
    return loads(fobj.read())
  File "C:\Python27\lib\site-packages\nginx.py", line 454, in loads
    if isinstance(lopen[0], Container):
IndexError: list index out of range
```