It seems like $input->getArgument('archive') can also be of type null and string[]; however, parameter $path of realpath() does only seem to accept string, maybe add an additional type check?
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Ignorable by Annotation
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If this is a false-positive, you can also ignore this issue in your code via the ignore-type annotation
Are you sure the assignment to $comment is correct as $archive->getComment() targeting wapmorgan\UnifiedArchive...edArchive::getComment() seems to always return null.
This check looks for function or method calls that always return null and whose
return value is assigned to a variable.