Refactor: remove redundant assertions and improve array handling #1152

Job	Run time
ci / PHPUnit (7.2, highest, ubuntu-latest, false)	17s
ci / PHPUnit (7.2, lowest, ubuntu-latest, false)	16s
ci / PHPUnit (7.3, highest, ubuntu-latest, false)	16s
ci / PHPUnit (7.3, lowest, ubuntu-latest, false)	16s
ci / PHPUnit (7.4, highest, ubuntu-latest, false)	17s
ci / PHPUnit (7.4, lowest, ubuntu-latest, false)	21s
ci / PHPUnit (8.0, highest, ubuntu-latest, false)	19s
ci / PHPUnit (8.0, lowest, ubuntu-latest, false)	22s
ci / PHPUnit (8.1, highest, ubuntu-latest, false)	17s
ci / PHPUnit (8.1, lowest, ubuntu-latest, false)	18s
ci / PHPUnit (8.2, highest, ubuntu-latest, false)	15s
ci / PHPUnit (8.2, lowest, ubuntu-latest, false)	23s
ci / PHPUnit (8.3, highest, ubuntu-latest, false)	21s
ci / PHPUnit (8.3, lowest, ubuntu-latest, false)	22s
ci / PHPUnit (8.4, windows-latest, highest, false)	1m 3s
ci / PHPUnit (8.4, ubuntu-latest, highest, false)	22s
ci / PHPUnit (8.4, ubuntu-latest, lowest, false)	13s
	5m 58s

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