fix(api): if domains field is empty clear the fqdn column

- providing an empty string for `domains` allows the ability to remove all URLs from the domains field

bootstrap/helpers/api.php

@@ -90,7 +90,7 @@ function sharedDataApplications()
         'is_auto_deploy_enabled' => 'boolean',
         'is_force_https_enabled' => 'boolean',
         'static_image' => Rule::enum(StaticImageTypes::class),
-        'domains' => 'string',
+        'domains' => 'string|nullable',
         'redirect' => Rule::enum(RedirectTypes::class),
         'git_commit_sha' => 'string',
         'docker_registry_image_name' => 'string|nullable',