Drupal 6 migration fails with TypeError: in_array(): Argument #2 ($haystack) must be of type array, string given in in_array()

Problem/Motivation

I want to migrate a Drupal 6 site to Drupal 9 with migrate_drupal module, but I get this error:

The website encountered an unexpected error. Please try again later.
TypeError: in_array(): Argument #2 ($haystack) must be of type array, string given in in_array() (line 106 of core/modules/node/src/Plugin/migrate/source/d7/NodeType.php).

Steps to reproduce

I fill the form in upgrade/credentials with this options:

• Drupal version: Drupal 6
• Database type: MariaDB
• DatabaseHost: mariadb (I work with wodby 4 drupal dockers so I use the service name)
• Databasename: Drupal6 (with capital letter)
• User: drupal
• password: drupal.
• document root: https://project_domain.es