If a Summary metadata field has an empty cell in Column A - where a metadata field name is expected - then an error is thrown when the standardisation tries to take the lower case value of a None value.
Actually, this error occurs with any non-string field header in Column A, not just empty ones. We check for non-strings and warn about them but then take lower of all values.
If a Summary metadata field has an empty cell in Column A - where a metadata field name is expected - then an error is thrown when the standardisation tries to take the lower case value of a None value.