MAINT: Fix descriptive stats with extension dtypes
MAINT: Fix descriptive stats with extension dtypes

Add special path for extension dtypes to remove N/A

statsmodels/statsmodels,bashtage/statsmodels,bashtage/statsmodels,josef-pkt/statsmodels,josef-pkt/statsmodels,josef-pkt/statsmodels,josef-pkt/statsmodels,statsmodels/statsmodels,josef-pkt/statsmodels,statsmodels/statsmodels,statsmodels/statsmodels,statsmodels/statsmodels,bashtage/statsmodels,josef-pkt/statsmodels,bashtage/statsmodels,bashtage/statsmodels,bashtage/statsmodels,statsmodels/statsmodels