`source_by_zip_path` does not need to return an `Option`

[Swatinem]

skip-changelog

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (3900ec0) 74.89% compared to head (d9c0d32) 74.89%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #828 +/- ## ======================================= Coverage 74.89% 74.89% ======================================= Files 63 63 Lines 15744 15745 +1 ======================================= + Hits 11792 11793 +1 Misses 3952 3952 ```