fix AssertionError on empty catalog

ProgressBar doesn't like having 0 as limit,
leading to an AssertionError.
Merge pull request #15 from JonnyJD/zero_progress

fix AssertionError on empty catalog
Bug fixes for releases with no format.

Signed-off-by: Ryan Helinski <rlhelinski@gmail.com>
Merging upstream changes and making bug fixes.

Signed-off-by: Ryan Helinski <rlhelinski@gmail.com>