Comment 1 for bug 1269780

=== modified file 'hooks/charmhelpers/fetch/__init__.py'
--- hooks/charmhelpers/fetch/__init__.py 2013-09-24 11:09:35 +0000
+++ hooks/charmhelpers/fetch/__init__.py 2014-01-16 12:20:51 +0000
@@ -117,8 +117,8 @@

     Note that 'null' (a.k.a. None) should not be quoted.
     """
- sources = safe_load(config(sources_var))
- keys = safe_load(config(keys_var))
+ sources = safe_load(config(sources_var)) or []
+ keys = safe_load(config(keys_var)) or []
     if isinstance(sources, basestring) and isinstance(keys, basestring):
         add_source(sources, keys)
     else: