Fixed bug handling a broken cached value.
diff --git a/httplib2/__init__.py b/httplib2/__init__.py
index a3ac4bf..8a55408 100644
--- a/httplib2/__init__.py
+++ b/httplib2/__init__.py
@@ -717,6 +717,7 @@
                 except:
                     self.cache.delete(cachekey)
                     cachekey = None
+                    cached_value = None
         else:
             cachekey = None
                     
@@ -728,7 +729,7 @@
             # RFC 2616 Section 13.10
             self.cache.delete(cachekey)
 
-        if method in ["GET", "HEAD"] and self.cache and 'range' not in headers:
+        if cached_value and method in ["GET", "HEAD"] and self.cache and 'range' not in headers:
             if info.has_key('-x-permanent-redirect-url'):
                 # Should cached permanent redirects be counted in our redirection count? For now, yes.
                 (response, new_content) = self.request(info['-x-permanent-redirect-url'], "GET", headers = headers, redirections = redirections - 1)