Add nullable attribute to lockScreenDismissalEnabled and lockScreenDismissalWarning

[FrankElias77]

Fixes #1813

Risk

This PR makes minor API changes.

Testing Plan

• I have verified that I have not introduced new warnings in this PR (or explain why below)
• I have run the unit tests with this PR
• I have tested this PR against Core and verified behavior (if applicable, if not applicable, explain why below).

Unit Tests

Unit tests added for the lockScreenDismissalWarning property.

Core Tests

N/A

Core version / branch / commit hash / module tested against: 7.0
HMI name / version / branch / commit hash / module tested against: N/A

Summary

Added the nullable attribute to mentioned properties.

Changelog

Breaking Changes

• N/A

Enhancements

• N/A

Bug Fixes

• Added the nullable attribute to mentioned properties.

Tasks Remaining:

N/A

CLA

• I have signed the CLA

[codecov]

Codecov Report

Merging #1822 into develop will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #1822      +/-   ##
===========================================
+ Coverage    84.61%   84.63%   +0.01%     
===========================================
  Files          418      418              
  Lines        20939    20939              
===========================================
+ Hits         17718    17721       +3     
+ Misses        3221     3218       -3