Fix fractional() formatting 0 as "0/1" instead of "0"

[Arunendra21]

Bug

fractional(0) returns "0/1", while every other whole number returns a bare number:

>>> import humanize
>>> humanize.fractional(0)
'0/1'      # expected '0'
>>> humanize.fractional(1)
'1'
>>> humanize.fractional(2)
'2'
>>> humanize.fractional(-2)
'-2'

Cause

The whole-number branch is gated on whole_number being truthy:

if whole_number and not numerator and denominator == 1:
    return f"{whole_number:.0f}"

whole_number is 0 (falsy) for the value 0, so it falls through to the if not whole_number: branch and is rendered as numerator/denominator = 0/1.

Fix

The branch only needs to check that no fractional part remains, i.e. numerator == 0, which is true for any whole number including 0. When the numerator is 0 the fraction is always 0/1, so the denominator == 1 check was redundant and is dropped.

Verified against all existing test_fractional cases (no changes) plus new cases for 0, 0.0 and "0".