Core/Packet Update structure (new format) for somes Items Opcode

This is not a C string you firstly have to read size, then the string:

    uint8 len = _worldPacket.ReadBits(8);
    BoxText = _worldPacket.ReadString(len);

See: https://github.com/TrinityCore/WowPacketParser/blob/master/WowPacketParserModule.V6_0_2_19033/Parsers/NpcHandler.cs#L66