TrinityCore/TrinityCore — comment on commit f4075f0f945c842fe2b1a08ea4a7fa253e8e2e53
File: src/server/game/Entities/Player/Player.cpp line 2310
By LihO:

group->RemoveMember(guid) is already being called before calling this function in Battleground.cpp ... this should fix it: http://paste2.org/p/1880201