From 57920a5808c03d7d035f592a13a71ba627fe85da Mon Sep 17 00:00:00 2001
From: Sharoon Thomas <sharoon.thomas@openlabs.co.in>
Date: Tue, 17 May 2011 11:41:12 -0400
Subject: [PATCH] Prevent pop if flashes not in session to avoid modification
 to session fixes #227

---
 flask/helpers.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/flask/helpers.py b/flask/helpers.py
index ec513d8f..a25dcadd 100644
--- a/flask/helpers.py
+++ b/flask/helpers.py
@@ -249,7 +249,8 @@ def get_flashed_messages(with_categories=False):
     """
     flashes = _request_ctx_stack.top.flashes
     if flashes is None:
-        _request_ctx_stack.top.flashes = flashes = session.pop('_flashes', [])
+        _request_ctx_stack.top.flashes = flashes = session.pop('_flashes') \
+            if '_flashes' in session else []
     if not with_categories:
         return [x[1] for x in flashes]
     return flashes