Float Nullability if Entire Column None

[typkrft]

Describe the bug
It seems that if all the values for a dataframe column are None, nullability throws an error. Not sure if theres a reason for this, or I am doing something wrong.

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of pandera.
• (optional) I have confirmed this bug exists on the main branch of pandera.

Note: Please read this guide detailing how to provide the necessary information for us to reproduce your bug.

Code Sample, a copy-pastable example

import pandas as pd 
import pandera as pa

df = pd.DataFrame({"test": [None, 1.1, None]})
df1=pd.DataFrame({"test": [None, None, None]})
schema = pa.DataFrameSchema(
    {"test": pa.Column(float, nullable=True)}
)
schema.validate(df)
print(df)
schema.validate(df1)
print(df1)

Expected behavior

I would expect the check to pass.

Desktop (please complete the following information):

• OS: [e.g. iOS] macOS 14.0 (23A344)
• Version: 0.19.3

[typkrft]

setting dtype=None in pa.Column seems to circumvent this, or explicitly setting the dtype in the dataframe prior to running validation.