Fix implicit nullables #240

Job	Run time
PHP-Linter (8.1) / linter	12s
PHP-Linter (8.3) / linter	16s
PHP-Linter (8.2) / linter	16s
Linter / json-linter	25s
PHP-Linter (8.4) / linter	13s
Linter / yaml-linter	4s
Linter / ecmascript-linter	-1s
Linter / style-linter	-1s
Unit tests, PHP 8.1, ubuntu-latest	23s
Unit tests, PHP 8.2, windows-latest	1m 8s
Unit tests, PHP 8.2, ubuntu-latest	17s
Unit tests, PHP 8.1, windows-latest	1m 0s
Unit tests, PHP 8.4, windows-latest	1m 4s
Unit tests, PHP 8.3, windows-latest	1m 14s
Unit tests, PHP 8.3, ubuntu-latest	18s
Unit tests, PHP 8.4, ubuntu-latest	17s
Quality control	0s
Security checks	0s
Code coverage	0s
Cleanup artifacts	0s
	7m 5s

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