Fix 0 extruders & bed compile (#20030)

buildroot/tests/rambo-tests

@@ -60,6 +60,16 @@ opt_enable USE_XMAX_PLUG USE_YMAX_PLUG USE_ZMAX_PLUG \
 opt_disable MIN_SOFTWARE_ENDSTOP_Z MAX_SOFTWARE_ENDSTOPS
 exec_test $1 $2 "Rambo CNC Configuration"
 
+#
+# Rambo heated bed only
+#
+restore_configs
+opt_set MOTHERBOARD BOARD_RAMBO
+opt_set EXTRUDERS 0
+opt_set TEMP_SENSOR_BED 1
+opt_enable REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER
+exec_test $1 $2 "Rambo heated bed only"
+
 #
 # Build with the default configurations
 #