Default button pin allocation on 1st boot.

wled00/cfg.cpp

@@ -169,14 +169,17 @@ bool deserializeConfig(JsonObject doc, bool fromFS) {
     }
   } else {
     // new install/missing configuration (button 0 has defaults)
-    if (fromFS)
-      for (uint8_t s=1; s<WLED_MAX_BUTTONS; s++) {
+    if (fromFS) {
+      uint8_t s=0;
+      if (pinManager.allocatePin(btnPin[0])) s++; // do not clear button 0 if pin successfully allocated
+      for (; s<WLED_MAX_BUTTONS; s++) {
         btnPin[s]           = -1;
         buttonType[s]       = BTN_TYPE_NONE;
         macroButton[s]      = 0;
         macroLongPress[s]   = 0;
         macroDoublePress[s] = 0;
       }
+    }
   }
   CJSON(touchThreshold,btn_obj[F("tt")]);
   CJSON(buttonPublishMqtt,btn_obj["mqtt"]);