🧑‍💻 Always return ActorResult on actor_run

[aleksul]

Change Summary

It's harder to write middlewares if actor's result can be none. This MR fixes it.

Checklist

• [x] Unit tests for the changes exist
• [x] Tests pass on CI and coverage remains at 100%
• [x] Documentation reflects the changes where applicable
• [x] My PR is ready to review

[codecov[bot]]

Codecov Report

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

Comparison is base (d4b52b2) 100.00% compared to head (3c6a170) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #147 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 61 61 Lines 2316 2310 -6 ========================================= - Hits 2316 2310 -6 ```

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