`download_demo` failing when `output_folder_path` is set

[fealho]

This issue pertains to the changes in a future SDV release (currently in the branch feature-branch-download-demo).

Problem Description

When downloading a demo dataset and setting an output folder path, the method raises an error:

data, meta = download_demo('single_table', 'student_placements_pii', 'output_folder')

KeyError: 'popitem(): dictionary is empty'

Expected behavior

When the output_folder_name is set, it should return the data and metadata in addition to writing data + metadata to that folder.