CAS user attribute resolve problem

Rocket.Chat Version: 0.52.0
Running Instances: 1
DB Replicaset OpLog:Disabled
Node Version:v4.5.0

when use wordpress CAS plugin，CAS server response xml below if user not have fitstname and lastname：

<cas:serviceResponse xmlns:cas="http://www.yale.edu/tp/cas">
  <cas:authenticationSuccess>
  <cas:user>aaaaaaaaaaa</cas:user>
  <cas:attributes>
    <cas:first_name/>
    <cas:last_name/>
    <cas:display_name>aaaaaaaaaaa</cas:display_name>
    <cas:user_email>535648741@qq.com</cas:user_email>
    <cas:user_url/>
  </cas:attributes>
  </cas:authenticationSuccess>
</cas:serviceResponse>  

Rocket chat will resolve attribute like:

debug Receveied response: { "username": "aaaaaaaaaaa", "attributes": { "first_name": [ "aaaaaaaaaaa535648741@qq.com" ] }, "PGTIOU": "", "ticket": "ST-YWFhYWFhYWFhYWF8aHR0cCUzQSUyRiUyRmNoYXQuaXY2LmNjJTJGX2NhcyUyRjVYdlBoUmR4b21aeVJDbml1fDE0ODg3NjUwOTkuNDA2Mnw0OWI0ZWI0MWFjZmQ3NDdhNmQyZmRjOTY2Y2IwNzk2OGQ4YzFiYTQ3", "proxies": [] }

Start by locating Rocket.Chat's CAS authentication and user-attribute parsing entry points, then reproduce the reported WordPress CAS response with empty first_name and last_name values. Compare the parsed attributes with the logged result and define completion as resolving the username, display name, and email without concatenating unrelated values.