1 Go to Studio, Create new LandingPage and add Form block.
2 Add to Form fe SingleLineText field and click on "Save form".

After this:
Code error:
`(500: Internal Server Error) - { "ErrorMessage": { "_media-type": "application\/vnd.formbuilder.api.ErrorMessage+json", "errorCode": 500, "errorMessage": "Internal Server Error", "errorDescription": "Warning: Invalid argument supplied for foreach()", "trace": "#0 \/var\/www\/ezstudio\/src\/EzSystems\/FormBuilderBundle\/lib\/Core\/REST\/Server\/Output\/ValueObjectVisitor\/Form.php(...`