PHP 8.4 Fix implicitly nullable parameter declarations deprecations

[Art4]

This PR fixes the PHP 8.4 deprecation warnings for implicitly nullable parameter declarations, see https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated

PHP 8.4 deprecates implicitly nullable types. PHP applications are recommended to explicitly declare the type as nullable. All type declarations that have a default value of null, but without declaring null in the type declaration emit a deprecation notice

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.47%. Comparing base (31768d5) to head (cc14f15).

Additional details and impacted files

@@            Coverage Diff            @@
##               v2.x     #407   +/-   ##
=========================================
  Coverage     98.47%   98.47%           
  Complexity      609      609           
=========================================
  Files            29       29           
  Lines          1841     1841           
=========================================
  Hits           1813     1813           
  Misses           28       28           

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