logger: fix unused variable build error
logger: fix unused variable build error

acfloria/Firmware,krbeverx/Firmware,PX4/Firmware,krbeverx/Firmware,krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,PX4/Firmware,krbeverx/Firmware,PX4/Firmware,PX4/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,PX4/Firmware,PX4/Firmware,krbeverx/Firmware,krbeverx/Firmware,acfloria/Firmware,PX4/Firmware