InvalidArgumentException: The state '' does not exist in workflow

In a content-moderated node, there is a multi-valued file field. Whatever state the node is in, whenever editing it, I can upload a file for the first time, but always fail afterwards. And there is a log message:
InvalidArgumentException: The state '' does not exist in workflow. in Drupal\workflows\Plugin\WorkflowTypeBase->getState() (line 155 of /var/www/myproject/web/core/modules/workflows/src/Plugin/WorkflowTypeBase.php).

Edit: not only multi-valued file field, but also the single-valued image field.