BUG: .mode(dropna=False) doesn't work with nullable integers

[theemathas]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd
series = pd.Series([1, 1, 2, 3]).astype('Int64')
print(series.mode(dropna=False))

Issue Description

This code causes the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/REDACTED/lib/python3.12/site-packages/pandas/core/series.py", line 2333, in mode
    res_values = values._mode(dropna=dropna)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/REDACTED/lib/python3.12/site-packages/pandas/core/arrays/masked.py", line 1112, in _mode
    result, res_mask = mode(self._data, dropna=dropna, mask=self._mask)
    ^^^^^^^^^^^^^^^^
ValueError: too many values to unpack (expected 2)

Expected Behavior

The code should print the modes of the input series.

Installed Versions

INSTALLED VERSIONS

commit : d9cdd2e
python : 3.12.3.final.0
python-bits : 64
OS : Darwin
OS-release : 23.4.0
Version : Darwin Kernel Version 23.4.0: Fri Mar 15 00:10:42 PDT 2024; root:xnu-10063.101.17~1/RELEASE_ARM64_T6000
machine : arm64
processor : arm
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.2.2
numpy : 1.26.4
pytz : 2024.1
dateutil : 2.9.0.post0
setuptools : None
pip : 24.0
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.4
IPython : 8.25.0
pandas_datareader : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.12.3
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : 3.1.3
pandas_gbq : None
pyarrow : None
pyreadstat : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : None
tzdata : 2024.1
qtpy : None
pyqt5 : None

[Aloqeely]

Thanks for the report! I can reproduce this on main, PRs to fix are welcome!

[halogen22]

take