OS: Windows 10 64bit
Empty "subject" (in "Edit XMP" / keywords) in XMP doesn show as "reuiered metadata" if marked "dc.subject_required=true" in xmp.ini
Effect: empty "subject" (keywords) in XMP does'nt show and work as "requiered metadata"
To reproduce:
1. close XnViewMP ver. 1.6.1
2. edit "xmp.ini" and ad line "dc.subject_required=true" (making "subject" as reuiered...)
3. save xmp.ini and restart XnViewMP 1.6.1
4. Edit image with ...Metadta/Edit XMP...
5. there is no name under Keywords "subject" given over the metadata field...
5. there is no red asterix "*" shown at the metadata field...
6. when saving image with empty "subject" can be saved without warning "requiered..."
Actual behaviour (bug): "subject" has no name, no red asterix, saving without warning when empty

Expected behaviour: show name "subject", show red asterix when "requiered" in xmp.ini, show warning at saving when "subject" empty
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Others, like iptc.ini and rest of xmp.ini works just fine! Well done!