oldSession.kick() in unique_session.go causes session.Bind() to fail

[kokais]

In Cluster mode, the frontend service reported some bind session error: "close closed session". When session.Bind is executed, unique_session.go will execute oldSession.Kick. If oldSession is closed, it will return that error:"close closed session".
So, my question is whether the "session.OnSessionBind" in unique_session.go does not need to return the error when oldSession.Kick, then session.Bind can bind the current uid normally.

[bruce1125]

Doing that may cover some bugs or issues for the server. The most important thing is to locate the problem and solve it.