disable join bg as group

diff --git a/src/server/game/Handlers/BattleGroundHandler.cpp b/src/server/game/Handlers/BattleGroundHandler.cpp
index db96c50..a574e44 100644
--- a/src/server/game/Handlers/BattleGroundHandler.cpp
+++ b/src/server/game/Handlers/BattleGroundHandler.cpp
@@ -84,6 +84,12 @@ void WorldSession::HandleBattlemasterJoinOpcode(WorldPacket& recvData)
     recvData >> instanceId;                                // instance id, 0 if First Available selected
     recvData >> joinAsGroup;                               // join as group

+    if (joinAsGroup)
+    {
+        ChatHandler(this).PSendSysMessage("You cannot join bg has group");
+        return;
+    }
+
     if (!sBattlemasterListStore.LookupEntry(bgTypeId_))
     {
         TC_LOG_ERROR("network", "Battleground: invalid bgtype (%u) received. possible cheater? player guid %u", bgTypeId_, _player->GetGUIDLow());