Incorrect salt generation when `counter = 0` (LessPass compatibility break)

[myau-def]

Description

There is a bug in salt generation when counter is set to 0. It breaks compatibility with the official LessPass implementation.

For any counter >= 1, the generated passwords match perfectly. However, for counter = 0, the generated passwords diverge.

Steps to Reproduce

With counter = 0 (Bug):

$ #lesspass "site" "login" "password" -C 0
pkwuO9<-W">g,Zag

$ lesspass-rs "site" "login" "password" -c 0
7q~o>vDo6n(Rf+"g

With counter >= 1 (Works correctly):

$ lesspass "site" "login" "password" -C 1
|KTnP2D^64'`q]Er

$ lesspass-rs "site" "login" "password" -c 1
|KTnP2D^64'`q]Er

$ lesspass "site" "login" "password" -C 2
b/f@D|kl2Rs:9k\^

$ lesspass-rs "site" "login" "password" -c 2
b/f@D|kl2Rs:9k\^

Root Cause

The issue is located in the generate_salt_to_uninit function (line 138). When counter is 0, the while counter != 0 loop condition is immediately false, so the loop never executes. As a result, it returns an empty buffer instead of "0".

let mut counter_buf = [MaybeUninit::uninit(); 8];
let counter = {
    let mut counter = counter as usize;
    let mut i = counter_buf.len();
    
    // This works for counter >= 1, but fails for counter = 0
    while counter != 0 {
        counter_buf[i - 1].write(b"0123456789abcdef"[counter & 0xf]);
        counter >>= 4;
        i -= 1;
    }

    &counter_buf[i..] // Returns an empty slice &[] when counter is 0
};