Fixed pickle unsaved document regression (#327)

docs/changelog.rst

@@ -2,6 +2,10 @@
 Changelog
 =========
 
+Changes in 0.8.1
+================
+- Fixed pickle unsaved document regression (#327)
+
 Changes in 0.8.0
 ================
 - Fixed querying ReferenceField custom_id (#317)

mongoengine/base/document.py

@@ -143,7 +143,8 @@ class BaseDocument(object):
     def __getstate__(self):
         data = {}
         for k in ('_changed_fields', '_initialised', '_created'):
-            data[k] = getattr(self, k)
+            if hasattr(self, k):
+                data[k] = getattr(self, k)
         data['_data'] = self.to_mongo()
         return data