TrinityCore/TrinityCore — comment on commit aea8b2af44aa7e8b15347c35a54180b806854c6c
File:  line 0
By elecyb:

Yes i see, happends when Player::RemoveFromWorld() is called (when switching continent or logout)
There is a check GetViewpoint() that expects NULL value returned.

Apply this until I found proper solution: https://gist.github.com/1556363