This PR is to apply after #6.
Fix the detection of empty header fields as the art dictionary contains all the usual header fields (more than 70, populated by innd). When empty, they have a None value.
In some places in the code, the detection was wrong (looking at the presence of the header field name in the dictionary instead of the presence of a value).
This PR is to apply after #6. Fix the detection of empty header fields as the
artdictionary contains all the usual header fields (more than 70, populated by innd). When empty, they have aNonevalue.In some places in the code, the detection was wrong (looking at the presence of the header field name in the dictionary instead of the presence of a value).