How to get rid of the apple-touch-icon request

I am building a client-server app with the ‘ESP8266 Thing Development Board’. The software stems from this example: Access Point (AP) Web Server.
In Safari it runs without problems on the iPhone 7. Even if the refresh rate of the page is set to 2 seconds (which i need for the final application) using this tag

<meta http-equiv='refresh' content='2'>

However, if you add the webpage as an app to the homescreen and activate it, the app loses in a few minutes its connection with the server.
The only diiference that I can see compared to the browser version is that as an app it request after each client request these png files

GET /apple-touch-icon-120x120-precomposed.png 
GET /apple-touch-icon-120x120.png 
GET /apple-touch-icon.png 
GET /apple-touch-icon.png

I tried different HTTP status response codes like
204 No Content
404 Not Found
410 Gone

But to no avail. The icon requests are still coming.
Does anyone has an idea how to get rid of these request?