Chocolatey Licensed source without authentication stops Chocolatey from working

[AdmiringWorm]

What You Are Seeing?

When running choco source add on the chocolatey.licensed source to for instance change it to allow self service. If you do so without adding a user and password switch to your command, Chocolatey CLI cannot be used after that.
What is Expected?

When authentication is not provided for the chocolatey.licensed source a 403 error would be desirable letting the user know of the error made.
How Did You Get This To Happen? (Steps to Reproduce)

Attempt to alter the chocolatey.licensed source via the following command choco source add --name="chocolatey.licensed" --source="https://licensedpackages.chocolatey.org/api/v2/" --allow-self-service
Then try running any Chocolatey CLI command, for instance choco
You get the following error output in shell: Value cannot be null. Parameter name: s

Output Log

N/A

Related issues

Followup from: chocolatey/chocolatey-licensed-issues#279

[vexx32]

Since this isn't a source users are expected to be fully setting up it might also be worth preventing users from modifying the user/password for this source (and maybe the url?) specifically and just letting them set the other configuration information. Maybe we just completely skip the setting of user/password when that source is updated by a user?

[AdmiringWorm]

@vexx32 something similar to that is already being worked on the licensed side, but instead of denying the users to modify the items it instead sets the values if they haven't already been set (either by reusing the previously configured values or with the hard-coded values we already know about).