TypeError: Argument 7 passed to Acquia\\ContentHubClient\\Settings::__construct() must be of the type array, null given

Steps to reproduce:

1. Create a Drupal project using BLT (& lightning)
2. Use composer to require drupal/acquia_contenthub:~2
3. Attempt to install the base content hub module

It appears that Content Hub is attempting to initiate a content hub creds before Content Hub has been configured. In the process, a null values is passed in for the webhook when the class is expecting an array.

I updated Drupal\acquia_contenthub\EventSubscriber\GetSettings::onGetSettings to pass an empty array for the webhook by default and that seemed to fix the issue.