Make some variables nullable

Makefile

@@ -1,10 +1,12 @@
+test: PHP := 8.0
 test: vendor
 	@echo "Run composer test (all tests)"
-	@docker run --rm -it --volume $$PWD:/app druidfi/drupal:php-8.0 composer test
+	@docker run --rm -it --volume $$PWD:/app druidfi/drupal:php-$(PHP) composer test
 
+test-%: PHP := 8.0
 test-%: vendor
 	@echo "Run composer test-$*"
-	@docker run --rm -it --volume $$PWD:/app druidfi/drupal:php-8.0 composer test-$*
+	@docker run --rm -it --volume $$PWD:/app druidfi/drupal:php-$(PHP) composer test-$*
 
 vendor:
 	composer install

src/DrupalEnvDetector.php

@@ -28,16 +28,16 @@ class DrupalEnvDetector
   ];
 
   private $app_env;
-  private array $config = [];
-  private array $config_directories = [];
-  private array $databases = [];
-  private $drupal_version = '';
+  private ?array $config = [];
+  private ?array $config_directories = [];
+  private ?array $databases = [];
+  private string $drupal_version = '';
 
   /**
    * @var EnvMappingAbstract
    */
   private $omen;
-  private array $settings = [];
+  private ?array $settings = [];
 
   public function __construct($settings_dir) {
     global $config, $config_directories, $databases, $settings;