[main] Fix RegexFilter NPE when useRawMsg is null (#3265 port)

[vpelikh]

Ports the fix from #3265 from the 2.x branch to main.

In the RegexFilter.createFilter() factory method, the useRawMsg parameter is declared as Boolean (boxed). When passed directly to the RegexFilter(boolean raw, ...) constructor, a null value causes an NPE during unboxing.

This change uses Boolean.TRUE.equals(useRawMsg) instead, which safely handles null by defaulting to false.

Changes

• log4j-core/.../filter/RegexFilter.java: Changed useRawMsg → Boolean.TRUE.equals(useRawMsg) in constructor call
• log4j-core-test/.../filter/RegexFilterTest.java: Added test ensuring no exception when useRawMsg is null

[ramanathan1504]

@vpelikh, Looks good, the fix and tests work perfectly locally and adapt well to the Log4j 3 variables.

However, we don't port changelog entries for direct syncs from 2.x to main. Please delete the changelog file (src/changelog/.3.x.x/3239_npe_fix_regex_filter_creator.xml). I'll merge this as soon as it's removed!

[vpelikh]

Thank you for the review, @ramanathan1504!

I've removed the changelog file from this PR. I also just went through all my other open backport PRs a few minutes ago and cleaned up the changelog entries there, so they should all be consistent now and won't cause any extra noise.

[ramanathan1504]

Thanks for the update, @vpelikh!

One quick request for the future: please try to avoid force-pushing when updating a PR. While it's fine for this because here there in no PR review comments, force-pushing erases the commit history and makes it very difficult for us to review iterative changes.

Everything else looks perfect. Thanks

[ramanathan1504]

@vpelikh
For future PRs, please make sure to check our Development Guidelines (BUILDING.adoc) and run ./mvnw verify (or at least ./mvnw spotless:apply) locally before committing. This will help catch these formatting errors before the CI does!