If you on Create New Item input a new item name with a space, e.g. "foo bar" and select GitHub Organization you get an immediate exception:

Caused by: java.io.FileNotFoundException: https://api.github.com/users/foo bar

There is no screen asking for the Organization or user credentials. If you input a job name without spaces there is no exception but it tries to connect to Github with the assumption that the job name is the Github Organization you want to connect to.