Fix when an initial value does not exist. See ietf-tools#739

 - Legacy-Id: 8104

Author: emiliosanchez

ietf/liaisons/widgets.py

@@ -89,7 +89,7 @@ def value_from_datadict(self, data, files, name):
 
     def render(self, name, value, attrs=None):
         html = u''
-        for liaison_id in value:
+        for liaison_id in value or []:
             liaison = LiaisonStatement.objects.get(pk=liaison_id)
             title = liaison.title
             if not title: