By clicking on the delete button on the fieldset sidebar, the fieldset can't be deleted.
Steps to Reproduce
- Go to Configuration > Control Panel > Instance Settings
- Change the instance language
- Go to Content & Data > Web Content > Structures
- Add a Structure and select to create a fieldset.
- Insert the instance language title
- Inset a text and numeric field and pt it on the structure.
- Click on the save button.
The fieldset is created properly.
The fieldset can't be created without an english fieldset title.