Due to an automatic refresh of the Tree view, any new group added is automatically then deleted as empty groups are removed during a refresh.
NOTE: Groups do not really exist! We use the "Group" field to display entries in a Tree like structure when the database is displayed in the Tree view (it is just another field when the database is displayed in List view). This group structure is built when the database is read on entering the correct master passphrase. Because it is built from the group field of the entries in the database, there can never be an empty group in the database.