Handle empty required list.

Added missing recipient.

src/saml2/assertion.py

@@ -270,7 +270,7 @@ def post_entity_categories(maps, **kwargs):
     restrictions = {}
     try:
         required = [d['friendly_name'].lower() for d in kwargs['required']]
-    except KeyError:
+    except (KeyError, TypeError):
         required = []
 
     if kwargs["mds"]:

src/saml2/server.py

@@ -532,7 +532,7 @@ class Server(Entity):
         to_sign = []
 
         if identity:
-            farg = self.update_farg(in_response_to, destination, farg=farg)
+            farg = self.update_farg(in_response_to, sp_entity_id, farg=farg)
 
             _issuer = self._issuer(issuer)
             ast = Assertion(identity)