Fix 500 when saving /site/edit without email
When saving /site/edit with no no_reply_email set, a 500 error page
would be returned due to an empty value being passed as value to
the datastore (which is not allowed for email fields).
README.txt
coverage.py
setup.py
coverage.egg-info/SOURCES.txt
coverage.egg-info/dependency_links.txt
coverage.egg-info/entry_points.txt
coverage.egg-info/top_level.txt