Redundant empty/null checks in mixed normalization

﻿From PHPStan baseline: src/div.php lines 8177-8183.

Snippet:
`
if (empty()) {
    return null;
}
if ( === null) {
    return null;
}
if (is_scalar() && (string)  === '') {
    return null;
}
`

PHPStan notes empty() already eliminates null/''/'0'/false/empty array. Evaluate whether these checks should be simplified to avoid dead branches.
