Fix bug in natural_sort_le

[Matistjati]

The current version has a subtle bug:

if ord('0') <= ord(a[i]) <= ord('9') and ord('0') <= ord(b[i]) <= ord('9'):

Should almost certainly be

if ord('0') <= ord(a[i]) <= ord('9') and ord('0') <= ord(b[j]) <= ord('9'):

(The index for b)

The old version can crash

def natural_sort_le(a: str, b: str) -> bool:
    a += '\0'
    b += '\0'
    i = j = 0

    def parse_num(s: str, i: int) -> tuple[int, int]:
        ret = 0
        while ord('0') <= ord(s[i]) <= ord('9'):
            ret = ret * 10 + ord(s[i]) - ord('0')
            i += 1
        return ret, i

    while i < len(a) and j < len(b):
        if ord('0') <= ord(a[i]) <= ord('9') and ord('0') <= ord(b[i]) <= ord('9'):
            anum, i = parse_num(a, i)
            bnum, j = parse_num(b, j)
            if anum == bnum:
                continue
            return anum < bnum
        if a[i] == b[j]:
            i += 1
            j += 1
            continue
        return a[i] < b[j]
    return True

print(natural_sort_le('00a0', '0a'))