Fatal error on config form with translation enabled when config is missing

Steps to reproduce:
* Create a new config form that modifies an custom configuration
* Create a route for the config form
* Make sure the custom_config doesn't exist in the active configuration
* Create a *.config_translation.yml for the custom configuration
* Go to the route for the config form

A fatal error occurs:
TypeError: Argument 2 passed to Drupal\Core\Config\TypedConfigManager::createFromNameAndData() must be of the type array, boolean given, called in /core/lib/Drupal/Core/Config/TypedConfigManager.php on line 78 in Drupal\Core\Config\TypedConfigManager->createFromNameAndData() (line 391 of core/lib/Drupal/Core/Config/TypedConfigManager.php).

This happens with Drupal 8.4.2 because the system tries to read the configuration, but since the data doesn't exist it returns FALSE, hence the error.