ThingerIO and ESP8266

If I complile my code this error occures:
C:\Users\USER\Documents\Arduino\libraries\thinger.io\src/ThingerWifi.h:47:5: warning: control reaches end of non-void function [-Wreturn-type]

The Telegram Bot that is icluded in this code works fine. But the implementation of https://thinger.io/ doesnt work because of the error message

#include <ThingerWifi.h>
#include <SPI.h>


#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>
#include <Wire.h>;

#include <ESP8266WiFi.h>
#include <WiFiClientSecure.h>
#include <UniversalTelegramBot.h> 
#include <ArduinoJson.h>
#include <ThingerESP8266.h>

const char* ssid = "Martin Router King";
const char* password = "paassword";

//thingerio diggi
#define USERNAME "username"
#define DEVICE_ID "id"
#define DEVICE_CREDENTIAL "credential"

ThingerESP8266 thing(USERNAME, DEVICE_ID, DEVICE_CREDENTIAL);


#define BOTtoken "botToken"

#define CHAT_ID "chat_id"

WiFiClientSecure client;
UniversalTelegramBot bot(BOTtoken, client);


int botRequestDelay = 1000;
unsigned long lastTimeBotRan;

float t, f, d;

Adafruit_BME280 bme;

// Handle what happens when you receive new messages
void handleNewMessages(int numNewMessages) {
  Serial.begin(115200);
  Serial.println("handleNewMessages");
  Serial.println(String(numNewMessages));
  bool status;
  status = bme.begin(0x76);

  for (int i=0; i<numNewMessages; i++) {
    // Chat id of the requester
    String chat_id = String(bot.messages[i].chat_id);
   if (chat_id != CHAT_ID){
      bot.sendMessage(chat_id, "Mit dir rede ich nicht!!! Du hast hier nix zu melden!!!", "");
      continue;
    }
    
    // Print the received message
    String text = bot.messages[i].text;
    Serial.println(text);

    String from_name = bot.messages[i].from_name;

    if (text == "/start") {
      String welcome = "Du hast also keine Lust auf nasse Wände? Gute Entscheidung!!!, " + from_name + ".\n";
      welcome += "Das kann ich bis jetzt für mehr Funktionen musst du mal Philip fragen. \nDer kann da bestimmt was drehn´ \n\n";
      welcome += "/temp  für die Temperatur im Badezimmer. \n";
      welcome += "/hum   für die aktuelle Luftfeuchtigkeit im Badezimmer. \n";
      welcome += "/druck für den Aktuellen Luftdruck im Badezimmer. \n";
      bot.sendMessage(chat_id, welcome, "");
    }

    if (text == "/temp") {
      t = bme.readTemperature();
      Serial.println("Temperaur abgefragt!");
      Serial.print(t);
      String messageTemp = "Die Temperatur beträgt gerade " + String(t) + "°C \n";
      bot.sendMessage(chat_id, messageTemp);
      
    }

    if(text == "/hum"){
      f = bme.readHumidity();
      Serial.println("Luftfeuchtigkeit abgefragt!");
      Serial.print(f);
      String messageHum = "Die Luftfeuchtigkeit liegt bei " + String(f) + "% \n";
      bot.sendMessage(chat_id, messageHum);
    }

    if(text == "/druck"){
      d = bme.readPressure();
      Serial.println("Luftdruck abgefragt!");
      Serial.print(d);
     // Serial.println("Luftdruck abgefragt!" +druck);
      bot.sendMessage(chat_id, "Der Luftdruck im Badezimmer beträgt: \n"); 
    }

  }
}

void setup() {
  Serial.begin(115200);

  #ifdef ESP8266
    client.setInsecure();
  #endif


  
  // Connect to Wi-Fi
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi..");
  }
  // Print ESP32 Local IP Address
  Serial.println(WiFi.localIP());

  thing.add_wifi(ssid, password);
  
  thing["Temperatur"] >> [](pson& out){
    out = bme.readTemperature();
  };
  
  thing["Luftfeuchtigkeit"] >> [](pson& out){
    out = bme.readHumidity();
  };
  thing["Luftdruck"] >> [](pson& out){
    out = bme.readPressure();
  };
 
}

void loop() {
  thing.handle();
  
  if (millis() > lastTimeBotRan + botRequestDelay)  {
    int numNewMessages = bot.getUpdates(bot.last_message_received + 1);

    while(numNewMessages) {
      Serial.println("got response");
      handleNewMessages(numNewMessages);
      numNewMessages = bot.getUpdates(bot.last_message_received + 1);
    }
    lastTimeBotRan = millis();
  }
}

That is a warning, not an error

Furthermore, what evidence do you have that it is the cause of the problem?

And that warning should include a location within the file. Still warning or error, it is not quite correct, but Windbill does have a point.