We were resetting the setting to its default if we had a NULL active provider

id. However, the only time it's valid to call

purple_credential_manager_set_active_provider with a NULL id is during shutdown.
If someone is trying to disable all credential providers, they will be selecting

the noop provider which has a non null id.

Ran and set the credential provider to libsecret. Closed the program, reopened, verified that libsecret was still selected.