fix: preserve null values in Validation::getValidated()

[michalsn]

Description
This PR fixes a validation bug where Validation::getValidated() could drop fields whose validated value was explicitly null.

The issue came from DotArrayFilter, which treated null like a missing key when building the validated data array. With this change, explicit null values are preserved, so validated output stays consistent with the original validated input, including cases such as permit_empty.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[neznaika0]

I hope that no one disrupts their work.

[neznaika0]

Did cs-fixer get new rules?

[michalsn]

@neznaika0 I guess a new version of cs-fix was released.

@paulbalandan Is that okay, or do we want to fix this another way?

[neznaika0]

Why did I ask, if you changed it manually, we decided that the prefix for @phpstan-* is not needed. Since this is an automatic update, we'll leave it for later.

[michalsn]

if you changed it manually

I did not change anything. The error popped up after rebase.

[paulbalandan]

php-cs-fixer has a new release with few new fixers and options. I think we should fix this separately. for psalm, I'm thinking of instead of separate phpstan-type and psalm-type, can we just type those in the @var directly instead of having separate phpstan-var and psalm-var?

[neznaika0]

@paulbalandan As I said, we discussed it in PR with you and came to the conclusion that we are so strongly attached to phpstan that we don't need to use prefixes. For psalm, I do not know if it has annotation differences.

[paulbalandan]

Yes, that's what I'm proposing here. I'll make a PR for the cs fixes and for psalm.