nathanmarz/cascalog — pull request #229 by f355 (2014-01-29 16:17:39+00:00)
Title: Allow empty vector to be used as a generator.

Fixes the issue that prevented `[]` to be used as a generator.
Due to the fact that `(seq [])` returns `nil`, following exception was thrown:
```
IllegalArgumentException No implementation of method: :generator of protocol: #'cascalog.cascading.types/IGenerator found for class: nil
```