`directories_next` provides different output to `dirs_next` when `%USERPROFILE%` is changed

[CLIDragon]

This issue came up while I was debugging an issue over on starship/starship#3526. When %USERPROFILE% is set to a non-null, invalid home directory, directories_next, but not dirs_next, fails to provide the correct home directory. This behaviour is consistent across dirs, dirs_next, directories and directories_next. What's strange is that directories and directories_next succeed when %USERPROFILE% is set to null, or a valid home directory that does not belong to the user (such as C:\Users\Default). They also seem to succeed when I set USERPROFILE using std::env::set_var, which is truly strange.

Here is the script I used to test the behaviour of dirs_next, directories_next, etc.

fn main() {
    let home_dir = directories_next::BaseDirs::new().map(|base_dirs| base_dirs.home_dir().to_owned());
    println!("Home directory (next): {:#?}", home_dir);

    let home_dir = dirs_next::home_dir();
    println!("Home dir (next): {:#?}", home_dir);

    let home_dir = directories::BaseDirs::new().map(|base_dirs| base_dirs.home_dir().to_owned());
    println!("Home directory: {:#?}", home_dir);

    let home_dir = dirs::home_dir();
    println!("Home dir: {:#?}", home_dir);
}

cargo.toml

[dependencies]
directories = "4.0.1"
directories-next = "2.0.0"
dirs = "4.0.0"
dirs-next = "2.0.0"