Clean up empty array check before return on on FilesFinder #30957

Job	Run time
PHPStan	1m 20s
Run with Space in Directory	28s
Commented Code	18s
Composer Validate	20s
Active Classes	20s
Compatible PHPStan versions	24s
Help and Version	19s
Preload php-parser Order	26s
Detect composer dependency issues	22s
Finalize classes	20s
PHP Linter	24s
Check no "*.php" files in rules Fixture directory	20s
Check before/after test fixture on no-changes	19s
	5m 40s

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