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

Once Disband() is called, the this pointer is deleted, and all players are set to a NULL group, so this check would not be true if Disband was succesfully called before this