Sid may be nil when testing with RSpec

Author: ryokdy

lib/aws/session_store/dynamo_db/rack_middleware.rb

@@ -37,6 +37,7 @@ def generate_unique_sid(env, session)
     end
 
     def write_session(req, sid, session, options)
+      sid = generate_sid if sid.nil? || !sid.respond_to?(:private_id)
       @lock.set_session_data(req.env, sid.private_id, session, options)
       sid
     end