Fixed #2611 -- Fixed XML serializer to handle null datetime fields. Thanks for reporting, csdurfee@gmail.com

git-svn-id: http://code.djangoproject.com/svn/django/trunk@3687 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/serializers/base.py

@@ -50,7 +50,11 @@ class Serializer(object):
         Convert a field's value to a string.
         """
         if isinstance(field, models.DateTimeField):
-            value = getattr(obj, field.name).strftime("%Y-%m-%d %H:%M:%S")
+            value = getattr(obj, field.name)
+            if value is None:
+                value = ''
+            else:
+                value = value.strftime("%Y-%m-%d %H:%M:%S")
         elif isinstance(field, models.FileField):
             value = getattr(obj, "get_%s_url" % field.name, lambda: None)()
         else: