Always handle subscription IDs in session.unsubscribe if provided

Author: OrKoN

index.bs

@@ -2102,7 +2102,7 @@ and will be removed in the future versions.
 <div algorithm="remote end steps for session.unsubscribe">
 The [=remote end steps=] with |session| and |command parameters| are:
 
-1. If |command parameters| matches the <code>session.UnsubscribeByAttributesRequest</code> production:
+1. If |command parameters| does not [=map/contain=] "<code>subscriptions</code>":
 
    1. Let |event names| be an empty [=/set=].