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).
# Want to get everything from the 'normal' models package.
from django.db.models import *
# The GeoManager
from django.contrib.gis.db.models.manager import GeoManager
# The GeoQ object
from django.contrib.gis.db.models.query import GeoQ
# The geographic-enabled fields.
from django.contrib.gis.db.models.fields import \
GeometryField, PointField, LineStringField, PolygonField, \
MultiPointField, MultiLineStringField, MultiPolygonField, \
GeometryCollectionField
# The geographic mixin class.
from mixin import GeoMixin