[Bug] Video section save failure (Validation error)

I want to be able to add video sections without the editor failing to save. Currently, adding '텍스트가 있는 비디오 (반전)' (Video with Text (Inverted)) or other video sections causes a '저장에 실패했습니다' (Failed to save) error, even if the section is later deleted. It seems the default placeholder is not passing validation, and the error state persists until a history rollback is performed. This is important because it prevents users from using video features and disrupts the editing workflow.