BUG: loc.setitem casting dtype to float with all false Indexer and rhs is an empty list

[phofl]

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

df = pd.DataFrame({"a": [1, 2]})

df.loc[[False, False]] = []

This also happens for multi block DataFrames

df = pd.DataFrame({"a": [1, 2], "b": "a"})

df.loc[[False, False], "a"] = []

Issue Description

   a
0  1.0
1  2.0

Expected Behavior

   a
0  1
1  2

Installed Versions

INSTALLED VERSIONS

commit : 68f763e
python : 3.8.12.final.0
python-bits : 64
OS : Linux
OS-release : 5.13.0-28-generic
Version : #31~20.04.1-Ubuntu SMP Wed Jan 19 14:08:10 UTC 2022
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 1.5.0.dev0+348.g68f763e753
numpy : 1.22.0
pytz : 2021.1
dateutil : 2.8.2
pip : 21.3.1
setuptools : 59.8.0
Cython : 0.29.24
pytest : 6.2.5
hypothesis : 6.23.1
sphinx : 4.2.0
blosc : None
feather : None
xlsxwriter : 3.0.1
lxml.etree : 4.6.3
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : 3.0.1
IPython : 7.28.0
pandas_datareader: None
bs4 : 4.10.0
bottleneck : 1.3.2
fastparquet : 0.7.1
fsspec : 2021.11.0
gcsfs : 2021.05.0
matplotlib : 3.4.3
numba : 0.53.1
numexpr : 2.7.3
odfpy : None
openpyxl : 3.0.9
pandas_gbq : None
pyarrow : 3.0.0
pyreadstat : 1.1.2
pyxlsb : None
s3fs : 2021.11.0
scipy : 1.7.2
sqlalchemy : 1.4.25
tables : 3.6.1
tabulate : 0.8.9
xarray : 0.18.0
xlrd : 2.0.1
xlwt : 1.3.0
zstandard : None
None

Process finished with exit code 0

[MichaelTiemannOSC]

The unbearable floatness of nullability (with apologies to The Unbearable Lightness of Being).

[andjhall]

take

[simonjayhawkins]

the same assignment a second time raises (on main)

df = pd.DataFrame({"a": [1, 2]})

df.loc[[False, False]] = []
df.loc[[False, False]] = []
# ValueError: shape mismatch: value array of shape (0,) could not be broadcast to indexing result of shape (0,1)