BUG: DataFrame.pivot mutates empty index.name attribute with typing._LiteralGenericAlias

[wesm]

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Reproducible Example

import pandas as pd
df = pd.DataFrame({
    'one': ['a', 'a', 'b', 'b', 'c', 'c', 'd', 'd'],
    'two': [0, 1, 0, 1, 0, 1, 0, 1],
    'three': [1, 2, 3, 4, 5, 6, 7, 8]
})
df.pivot(index='one', columns='two', values='three')
df.index.name

Issue Description

The above code sample produces typing.Literal[<no_default>]. I would expect df.index.name to not be modified by DataFrame.pivot. This is a regression for earlier versions of pandas.

Expected Behavior

In earlier versions of pandas the output is None.

Installed Versions

INSTALLED VERSIONS

commit : 478d340
python : 3.10.10.final.0
python-bits : 64
OS : Darwin
OS-release : 22.3.0
Version : Darwin Kernel Version 22.3.0: Mon Jan 30 20:38:37 PST 2023; root:xnu-8792.81.3~2/RELEASE_ARM64_T6000
machine : x86_64
processor : i386
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.0.0
numpy : 1.23.5
pytz : 2023.3
dateutil : 2.8.2
setuptools : 67.6.1
pip : 23.0.1
Cython : 0.29.34
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.9.2
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 7.31.1
pandas_datareader: 0.10.0
bs4 : 4.12.0
bottleneck : None
brotli :
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.7.1
numba : 0.56.4
numexpr : 2.8.4
odfpy : None
openpyxl : 3.1.1
pandas_gbq : None
pyarrow : 11.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : 1.10.1
snappy : None
sqlalchemy : 2.0.8
tables : 3.7.0
tabulate : None
xarray : None
xlrd : 2.0.1
zstandard : None
tzdata : 2023.3
qtpy : 2.3.1
pyqt5 : None