You may not have a favicon.ico file, but this happens if someone inserted a call to the favicon.ico file and it isn’t there, this causes a 404 error and in this case it looks like you have a custom 404 error page (did you create one ?)
This 404 page redirects to searchdonor.com, see image, so I don’t know if this is the redirect mentioned. Trying to connect to searchdonor.com results in another avast alert (malicious URL), image 2.
So it does look like that 404 page is the cause of the alert.