This is in the 4.7 upgrade where we transfer the Global extra's to the cats table.
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For whatever reason I can't say why your's did not transfer. However to get those to show again it should be as simple to retype in the Edit Cats page for the parent cat the Global extra names you had in order and apply to all children. Your extra's should all reappear as the data is still there from your photos table so you just need to reapply those names to the cats and it will show.