[SYS] Avoid AP generation if no WiFi and config already entered

For security reason do not generate an Access Point if the configuration has been entered and if the WiFi is not detected at start

main/main.ino

@@ -1835,6 +1835,16 @@ void setup_wifimanager(bool reset_settings) {
   //set minimum quality of signal so it ignores AP's under that quality
   wifiManager.setMinimumSignalQuality(MinimumWifiSignalQuality);
 
+  if (SPIFFS.begin()) {
+    Log.trace(F("mounted file system" CR));
+    // Check if the config file exists and prevent the portal from showing if yes
+    // Showing the portal if the config file exist would enable access to the configuration data and to the ESP update page
+    // This is a security risk if an attacker has access to the gateway password
+    if (SPIFFS.exists("/config.json")) {
+      wifiManager.setEnableConfigPortal(false);
+    }
+  }
+
 #  ifdef ESP32_ETHERNET
   wifiManager.setBreakAfterConfig(true); // If ethernet is used, we don't want to block the connection by keeping the portal up
 #  endif