[Bug] FutureWarning with the behavior of DataFrame concatenation with empty or all-NA entries

[lisphilar]

Checkbox

• I agree to follow code of conduct and to engage in discussion actively.
• I agree to create a new issue with the other templates if this is not a bug.
• I used the latest version of covsirphy.

Summary

Test workflow raised the following warning and this is ignorable because the loc_df of the the lass can accepts object type for processing.

https://github.com/lisphilar/covid19-sir/actions/runs/6063719611/job/16451377196

Reproducible example script

NA

The current outputs

FutureWarning: The behavior of DataFrame concatenation with empty or all-NA entries is deprecated. In a future version, this will no longer exclude empty or all-NA columns when determining the result dtypes. To retain the old behavior, exclude the relevant entries before the concat operation.

Expected outputs

No errors.

Environment

- CovsirPhy version: 3.0.0
- Python version: 3.11.0

Package manager (required if installation issue)

No response

Platform (required if installation issue)

No response

Additional Context

pandas-dev/pandas#45637