🔧 Board temp sensor check

Marlin/src/inc/SanityCheck.h

   #error "CONTROLLER_FAN_MIN_BOARD_TEMP requires TEMP_SENSOR_BOARD."
 #endif
 
+#if TEMP_SENSOR_BOARD && !PIN_EXISTS(TEMP_BOARD)
+  #error "TEMP_SENSOR_BOARD requires TEMP_BOARD_PIN."
+#endif
+
 #if ENABLED(LASER_COOLANT_FLOW_METER) && !(PIN_EXISTS(FLOWMETER) && ENABLED(LASER_FEATURE))
   #error "LASER_COOLANT_FLOW_METER requires FLOWMETER_PIN and LASER_FEATURE."
 #endif