Behavior Override Fix

[Eric-Vin]

Description

Fixes the bug in Issue https://github.com/BerkeleyLearnVerify/Scenic/issues/222 , where one had issues overriding behavior if it was set to None. Also fixed a bug where the lastActions property wasn't being set properly, and added various tests.

Issue Link

https://github.com/BerkeleyLearnVerify/Scenic/issues/222

Checklist

• [X] I have tested the changes locally via pytest and/or other means
• [X] I have added or updated relevant documentation
• [X] I have autoformatted the code with black and isort
• [X] I have added test cases (if applicable)

Additional Notes

N/A

[codecov[bot]]

Codecov Report

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

Project coverage is 86.16%. Comparing base (9da70c3) to head (ad0b7ad). Report is 9 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #252 +/- ## ========================================== + Coverage 86.14% 86.16% +0.01% ========================================== Files 144 144 Lines 24991 25117 +126 ========================================== + Hits 21529 21642 +113 - Misses 3462 3475 +13 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.