AP_BattMonitor: fix compilation when scripting in but scripted-battery out #35691

Job	Run time
build (stm32f7, chibios, 10)	14m 8s
build (stm32h7, chibios, 10)	12m 45s
build (fmuv2-plane, chibios, 10)	5m 45s
build (periph-build, chibios, 10)	19m 3s
build (iofirmware, chibios, 10)	2m 27s
build (CubeOrange-bootloader, chibios, 10)	1m 10s
build (fmuv3-bootloader, chibios, 10)	1m 29s
build (revo-bootloader, chibios, 10)	1m 25s
build (stm32h7-debug, chibios, 10)	6m 52s
build (fmuv3, chibios, 10)	13m 26s
build (revo-mini, chibios, 10)	10m 42s
build (MatekF405-Wing, chibios, 10)	11m 17s
build (CubeOrange-ODID, chibios, 10)	8m 9s
build (CubeRedPrimary-bootloader, chibios, 10)	1m 14s
build (configure-all, chibios, 10)	9m 23s
build (build-options-defaults-test, chibios, 10)	19m 40s
build (signing, chibios, 10)	9m 33s
build (CubeOrange-PPP, chibios, 10)	6m 47s
build (CubeOrange-SOHW, chibios, 10)	7m 18s
build (Pixhawk6X-PPPGW, chibios, 10)	3m 16s
	2h 45m 49s

Provide feedback