if no previous version, load Before must return None, this should fix

bug about loadBefore noticed in mechanize test


git-svn-id: https://svn.erp5.org/repos/neo/branches/prototype3@177 71dcc9de-d417-0410-9af5-da40c76e7ee4

neo/client/app.py

@@ -375,7 +375,12 @@ class Application(object):
         if tid is None:
             tid = INVALID_TID
         logging.debug('loading %s before %s', dump(oid), dump(tid))
-        return self._load(oid, tid)
+        data, start, end = self._load(oid, tid)
+        if end is None:
+            # No previous version
+            return None
+        else:
+            return data, start, end
 
 
     def tpc_begin(self, transaction, tid=None, status=' '):