scrapy/scrapy — pull request #750 by oliverrahner (2014-06-17 08:56:35+00:00)
Title: Update python.py

When coming from FormRequest.from_response, unicode_to_str is called. If there is a form field with no value, the method is called with text = None.
Because it makes sense for these functions to be more robust, I chose to check for this case here.