Cannot subscribe to public urls

[mdavis-xyz]

I want to subscribe to a public calendar such as this one. Since it's public it does not require a username or password. (I can successfully sync it without a username or password on Thunderbird.) If I try to do so through this app, the app tells me "this field is required".

Can you please make the username and password fields optional?

[strk]

doesn't this fail anyway by passing fake username/password fields ? I think it's a similar case to #258