Fixed #4330 -- Fixed typo when retrieving field names. Patch from Marc Fargas.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5293 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/formtools/preview.py

@@ -83,7 +83,7 @@ class FormPreview(object):
         """
         while 1:
             try:
-                f = self.form.fields[name]
+                f = self.form.base_fields[name]
             except KeyError:
                 break # This field name isn't being used by the form.
             name += '_'