Fix setting of default values

src/Handler.php

@@ -227,7 +227,7 @@ class Handler extends BaseHandler {
         $env->put('COMPOSE_PROJECT_NAME', $projectname);
       }
       $extra = $this->composer->getPackage()->getExtra() + ['docker4drupal' => []];
-      $options = NestedArray::mergeDeep([
+      $options = NestedArray::mergeDeep($extra['docker4drupal'], [
         'projectname' => $projectname,
         'ci_home' => '/home/gitlab-runner',
         'docker0' => [
@@ -309,7 +309,7 @@ class Handler extends BaseHandler {
         'wkhtmltox' => [
           'enable' => 0,
         ],
-      ], $extra['docker4drupal']);
+      ]);
 
       if ($this->isCiContext() || $this->isLocalDevMode()) {
         $projectRoot = $this->getDockerMountSource(getenv('CI_PROJECT_DIR'));