Switching toolhead array access protection

[GMagician]

Should fix #23980

[GMagician]

Can't find out which cnf is used to see why it doesn't compile

[ellensp]

In buildroot/tests/BIGTREE_GTR_V1_0

It uses the bugfix default config then modifies it with

restore_configs
opt_set MOTHERBOARD BOARD_BTT_GTR_V1_0 SERIAL_PORT -1 \
        EXTRUDERS 3 TEMP_SENSOR_1 1 TEMP_SENSOR_2 1 \
        SERVO_DELAY '{ 300, 300, 300 }'
opt_enable SWITCHING_TOOLHEAD TOOL_SENSOR
exec_test $1 $2 "BigTreeTech GTR | Switching Toolhead | Tool Sensors" "$3"

so it probably needs a SWITCHING_TOOLHEAD_X_POS '{ 215, 0 ,0}' added to opt_set

[ellensp]

Needs a \ on end of the previous line. the opt_set is one line split over several actual lines

[GMagician]

Yep, just made quickly and not take too much care of what I've done. Thanks for note