Fixed WS281x output on ESP32

Fixed potential out-of-bounds write in MQTT
Fixed IR pin not changeable if IR disabled
Fixed XML API <wv> containing -1 on Manual only RGBW mode (see #888, #1783)

wled00/mqtt.cpp

@@ -64,9 +64,9 @@ void onMqttMessage(char* topic, char* payload, AsyncMqttClientMessageProperties
   }
   //make a copy of the payload to 0-terminate it
   char* payloadStr = new char[len+1];
+  if (payloadStr == nullptr) return; //no mem
   strncpy(payloadStr, payload, len);
   payloadStr[len] = '\0';
-  if (payloadStr == nullptr) return; //no mem
   DEBUG_PRINTLN(payloadStr);
 
   size_t topicPrefixLen = strlen(mqttDeviceTopic);