Credentials aren't required to create a Client

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@6306 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/main/as/com/threerings/crowd/client/CrowdClient.as

@@ -38,7 +38,7 @@ public class CrowdClient extends Client
     BodyMarshaller;
     CrowdPermissionPolicy;
 
-    public function CrowdClient (creds :Credentials)
+    public function CrowdClient (creds :Credentials = null)
     {
         super(creds);
     }

src/main/as/com/threerings/presents/client/Client.as

@@ -57,7 +57,7 @@ public class Client extends EventDispatcher
     // statically reference classes we require
     TimeBaseMarshaller;
 
-    public function Client (creds :Credentials)
+    public function Client (creds :Credentials = null)
     {
         _creds = creds;
     }