handle wrong webaddress

[matititam]

https://wokwi.com/arduino/projects/287311734683730445Hi

accidentally, I had shared a link with the "Hi" attached. I would expect the site to tell that something is wrong with the address or better let me choose option to go to home page or https://wokwi.com/arduino/projects/287311734683730445

[urish]

Fixed! We now show a proper 404 error page