Override hash_salt when empty vs not set.

https://github.com/drupal/drupal/blob/9.4.x/core/assets/scaffold/files/default.settings.php\#L252

web/sites/default/settings.platformsh.php

@@ -108,7 +108,7 @@
 
  // Set the project-specific entropy value, used for generating one-time
  // keys and such.
- $settings['hash_salt'] = $settings['hash_salt'] ?? $platformsh->projectEntropy;
+ $settings['hash_salt'] = !empty($settings['hash_salt']) ? $platformsh->projectEntropy : '';
 
  // Set the deployment identifier, which is used by some Drupal cache systems.
  $settings['deployment_identifier'] = $settings['deployment_identifier'] ?? $platformsh->treeId;