Fix for wled#3991

Author: blazoncek

wled00/json.cpp

@@ -598,7 +598,7 @@ void serializeState(JsonObject root, bool forPreset, bool includeBri, bool segme
     nl["dur"] = nightlightDelayMins;
     nl["mode"] = nightlightMode;
     nl[F("tbri")] = nightlightTargetBri;
-    nl[F("rem")] = nightlightActive ? (nightlightDelayMs - (millis() - nightlightStartTime)) / 1000 : -1; // seconds remaining
+    nl[F("rem")] = nightlightActive ? (int)(nightlightDelayMs - (millis() - nightlightStartTime)) / 1000 : -1; // seconds remaining
 
     JsonObject udpn = root.createNestedObject("udpn");
     udpn[F("send")] = sendNotificationsRT;