Fix broken autocomplete

SublimeHaskell fails to load properly when Sublime is started due to a typo.

It fails with this exception;

```
Sublime Haskell: reinspecting project (/Users/kolmodin/code/binary-bits)
Exception in thread Thread-3:
Traceback (most recent call last):
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/threading.py", line 532, in __bootstrap_inner
    self.run()
  File "./autocomplete.py", line 943, in run
  File "./autocomplete.py", line 1004, in _refresh_all_module_info
  File "./autocomplete.py", line 1050, in _refresh_module_info
  File "./sublime_haskell_common.py", line 373, in get_source_dir
UnboundLocalError: local variable 'i' referenced before assignment
```