Fix: Null Pointer Exception in PublishSettingsViewModel

[zwarm]

Fixes #20272

This PR fixes a NPE when accessing EditPostRepository.dateCreated. The getter for dateCreated uses a post!! which will throw a NPE if the post is null. This PR replaces the use of let with takeIf { it.hasPost() } to ensure we don't call dateCreated when there is no post.

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To Test:

I was unable to recreate the issue, but did write a unit test to validate the new takeIf logic.
Please verify that all unit tests pass CI

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Regression Notes

1. Potential unintended areas of impact
   Continue to experience the NPE crash

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   Add unit test to EditPostPublishSettingsViewModelTest

3. What automated tests I added (or what prevented me from doing so)
   N/A

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PR Submission Checklist:

• I have completed the Regression Notes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

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Testing Checklist (strike-out the not-applying and unnecessary ones): N/A

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	App Name	WordPress
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[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 40.62%. Comparing base (3be32da) to head (96460b9).

❗ Current head 96460b9 differs from pull request most recent head 980cb73. Consider uploading reports for the commit 980cb73 to get more accurate results

Files	Patch %	Lines
...press/android/ui/posts/PublishSettingsViewModel.kt	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            trunk   #20745   +/-   ##
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  Coverage   40.62%   40.62%           
=======================================
  Files        1489     1489           
  Lines       68531    68532    +1     
  Branches    11326    11326           
=======================================
+ Hits        27841    27842    +1     
  Misses      38161    38161           
  Partials     2529     2529           

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[AjeshRPai]

Hey @zwarm

Changes LGTM, I couldn't reproduce the crash as well but your changes makes sense. Did a minor formatting in commit 980cb73

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud