How to detect 'empty' keys when read parquet file using dex mapping

Dear Community,

I’m using the following dex mapping :

<AimmsParquetMapping>

    <RowMapping name="xxx">
    <ColumnMapping name="A" binds-to="iA" binds-existing="1" skip-non-existing="0"/>
    <ColumnMapping name="B" binds-to="iB"/>
     <ColumnMapping name="C" maps-to="plan(iA,iB)"/>
    </RowMapping>
</AimmsParquetMapping>

Suppose now I have a row in the input file that has a NULL for the iA value. I would expect an error when reading the file, since NULL is not in the set, but the line just got skipped. Is there something wrong here or is there another way to detect empty key values?

Kind regards,

Marc

Using DEX version: 25.6.1.1