Move common strings (#20846)

Marlin/src/module/settings.cpp

@@ -176,8 +176,6 @@ static const uint32_t   _DMA[] PROGMEM = DEFAULT_MAX_ACCELERATION;
 static const float     _DASU[] PROGMEM = DEFAULT_AXIS_STEPS_PER_UNIT;
 static const feedRate_t _DMF[] PROGMEM = DEFAULT_MAX_FEEDRATE;
 
-extern const char SP_X_STR[], SP_Y_STR[], SP_Z_STR[], SP_E_STR[];
-
 /**
  * Current EEPROM Layout
  *
@@ -3181,7 +3179,7 @@ void MarlinSettings::reset() {
 
       #elif ENABLED(AUTO_BED_LEVELING_UBL)
 
-        config_heading(forReplay, PSTR(""), false);
+        config_heading(forReplay, NUL_STR, false);
         if (!forReplay) {
           ubl.echo_name();
           SERIAL_CHAR(':');