Fixed #8194: `AdminForm.first_field` now correctly returns the first field when using custom field orders.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8681 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/admin/helpers.py

@@ -20,8 +20,10 @@ class AdminForm(object):
             yield Fieldset(self.form, name, **options)
 
     def first_field(self):
-        for bf in self.form:
-            return bf
+        if self.form._meta.fields is not None:
+            name = self.form._meta.fields[0]
+            return forms.BoundField(self.form, self.form.fields[name], name)
+        return iter(self.form).next()
 
     def _media(self):
         media = self.form.media