Core/ObjectMgr: Refactor guild related functions into dedicated class

src/server/game/Server/WorldSession.cpp

@@ -30,6 +30,7 @@
 #include "Player.h"
 #include "Vehicle.h"
 #include "ObjectMgr.h"
+#include "GuildMgr.h"
 #include "Group.h"
 #include "Guild.h"
 #include "World.h"
@@ -437,7 +438,7 @@ void WorldSession::LogoutPlayer(bool Save)
             HandleMoveWorldportAckOpcode();
 
         ///- If the player is in a guild, update the guild roster and broadcast a logout message to other guild members
-        if (Guild *pGuild = sObjectMgr->GetGuildById(_player->GetGuildId()))
+        if (Guild *pGuild = sGuildMgr->GetGuildById(_player->GetGuildId()))
             pGuild->HandleMemberLogout(this);
 
         ///- Remove pet