From 22c75cf7486cbce8db3d06aa255e8e5db76e4d9c Mon Sep 17 00:00:00 2001
From: ichuang <ichuang@gmail.com>
Date: Thu, 17 May 2012 22:39:20 -0400
Subject: [PATCH] make courseware/capa/util.py contextualize_text return
 gracefully if text = None

---
 djangoapps/courseware/capa/util.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/djangoapps/courseware/capa/util.py b/djangoapps/courseware/capa/util.py
index b85073d78c..d042aa21d3 100644
--- a/djangoapps/courseware/capa/util.py
+++ b/djangoapps/courseware/capa/util.py
@@ -1,6 +1,7 @@
 def contextualize_text(text, context): # private
     ''' Takes a string with variables. E.g. $a+$b. 
     Does a substitution of those variables from the context '''
+    if not text: return text
     for key in sorted(context, lambda x,y:cmp(len(y),len(x))):
         text=text.replace('$'+key, str(context[key]))
     return text