Out-of-bounds read in DZG_GSH01 SLIP CRC parser can crash powermeter driver

EVerest is an EV charging software stack. Prior to version 2025.12.0, `is_message_crc_correct` in the DZG_GSH01 powermeter SLIP parser reads `vec[vec.size()-1]` and `vec[vec.size()-2]` without checking that at least two bytes are present. Malformed SLIP frames on the serial link can reach `is_message_crc_correct` with `vec.size() < 2` (only via the multi-message path), causing an out-of-bounds read before CRC verification and `pop_back` underflow. Therefore, an attacker controlling the serial input can reliably crash the process. Version 2025.12.0 fixes the issue.