Core/Arena: Fix exploit on delete member with team during fights.

src/server/game/Handlers/ArenaTeamHandler.cpp

@@ -311,6 +311,10 @@ void WorldSession::HandleArenaTeamRemoveOpcode(WorldPacket& recvData)
         SendArenaTeamCommandResult(ERR_ARENA_TEAM_QUIT_S, "", "", ERR_ARENA_TEAM_LEADER_LEAVE_S);
         return;
     }
+    
+    // Player cannot be removed during fights
+    if (arenaTeam->IsFighting())
+        return;
 
     arenaTeam->DelMember(member->Guid, true);