Show default MQTT user and password in WebUI

code/espurna/mqtt.ino

@@ -304,9 +304,9 @@ void _mqttWebSocketOnSend(JsonObject& root) {
     root["mqttEnabled"] = mqttEnabled();
     root["mqttServer"] = getSetting("mqttServer", MQTT_SERVER);
     root["mqttPort"] = getSetting("mqttPort", MQTT_PORT);
-    root["mqttUser"] = getSetting("mqttUser");
+    root["mqttUser"] = getSetting("mqttUser", MQTT_USER);
     root["mqttClientID"] = getSetting("mqttClientID");
-    root["mqttPassword"] = getSetting("mqttPassword");
+    root["mqttPassword"] = getSetting("mqttPassword", MQTT_PASS);
     root["mqttKeep"] = _mqtt_keepalive;
     root["mqttRetain"] = _mqtt_retain;
     root["mqttQoS"] = _mqtt_qos;