Fix M503 S parameter

Marlin/Marlin_main.cpp

@@ -9917,7 +9917,7 @@ inline void gcode_M502() {
    * M503: print settings currently in memory
    */
   inline void gcode_M503() {
-    (void)settings.report(parser.boolval('S'));
+    (void)settings.report(parser.seen('S') && !parser.value_bool());
   }
 #endif
 

Marlin/configuration_store.cpp

@@ -1547,7 +1547,7 @@ void MarlinSettings::reset() {
    *
    * Unless specifically disabled, M503 is available even without EEPROM
    */
-  void MarlinSettings::report(bool forReplay) {
+  void MarlinSettings::report(const bool forReplay) {
 
     /**
      * Announce current units, in case inches are being displayed

Marlin/configuration_store.h

@@ -52,10 +52,10 @@ class MarlinSettings {
     #endif
 
     #if DISABLED(DISABLE_M503)
-      static void report(bool forReplay=false);
+      static void report(const bool forReplay=false);
     #else
       FORCE_INLINE
-      static void report(bool forReplay=false) { UNUSED(forReplay); }
+      static void report(const bool forReplay=false) { UNUSED(forReplay); }
     #endif
 
   private: