The attached log file is about viewing an image in the viewer, with the category panel active, and trying to insert a child category (from within a user-defined tab) without success. Can you verify if this is a bug? Thanks!
I will check this for one of the next releases.
Until then I suggest you add new categories in the Category View or Category Panel.
Fixed for the next release.
Thanks for bringing this to my attention. Many things are 'special' in the Viewer and require special handling.
You're welcome & thank you for correcting this problem.
Another bug bites the dust :D