Credentials flow and refresh_token: IndexError Exception

[tbronson]

While using the credentials flow (app permissions), refresh_token can fail with an IndexError.

connection.py line 884

result = self.msal_client.acquire_token_silent_with_error(
            scopes=scopes,
            account=self.msal_client.get_accounts(username=self.username)[0],
        )

get_accounts can and does return an empty list when using app credentials, rather than delegated user credentials