Url parse incorrect logic

[HO-COOH]

See here

If we construct a url with

    minio::s3::BaseUrl base_url{ "https://1.2.3.4" };

Then the std::getline call will return the entire string "1.2.3.4" then std::stoi("1.2.3.4") returns 1 as port, which is obviously wrong. It should simply NOT parse the port if : is not found in the url, and let user specify.