Error saving series with all missing values

[greg-wiltshire]

Bug Report

Steps to Reproduce:

In an IDE using the tracdap runtime try to save a dataFrame as an output of a model:

Create the dataFrame with a column made up completely of missing values:

data = {
    'INDEX': ['A', 'B', 'C'],
    'INDEX_VALUE_DATE': [date, date, date],
    'INDEX_VALUE': [pd.NA, pd.NA, pd.NA]
}

df = pd.DataFrame(data)

With the schema:

field_name,field_type,label,categorical,business_key,format_code
INDEX,STRING,Index name,FALSE,FALSE
INDEX_VALUE_DATE,DATE,Index value date,FALSE,FALSE,"DAY"
INDEX_VALUE,FLOAT,Index value,FALSE,FALSE,"|.|3|||1"

Expected Result:

Data is saved as an output without error.

Actual Result:

Error occurs

    raise _ex.EModelExec(msg) from e
tracdap.rt.exceptions.EModelExec: There was an unhandled error in the model: Column 2 named INDEX_VALUE expected length 3 but got length 0

Environment:

Python 3.11
tracdap runtime 0.5.9

Additional Context:

Saving the data works if one value in the column is not NA.