Add state form doesn't work

Step to reproduce:

1. Go to Administer -> Workflow.
2. Click on "Add state" on a workflow to add a state to that workflow.
3. Uncheck some checkboxes and click Submit.

In the newly created state the formerly unchecked checkboxes are checked again.
Click on "Add state" again and the formerly unchecked checkboxes are unchecked.

In the database, in workflow_fields table, you'll find records with sid = 0 instead of the id of the newly created state.