[9.x] Conditionable should return HigherOrderWhenProxy only when the args number is exactly 1

[leo108]

$extraFilter = $condition ? null : function ($query) { $query->where('field', 'value'); };
$query = User::query()->when($extraFilter !== null, $extraFilter);

// When $condition is false, which means $extraFilter is null
// Before: Illuminate\Support\HigherOrderWhenProxy
// After: Illuminate\Database\Eloquent\Builder
dump(get_class($query));

[BrandonSurowiec]

A simple test should be added.

[leo108]

@BrandonSurowiec Done