[KPhotoAlbum] Keywords with id=0?

[Johannes Zarl-Zierl]

Am Samstag, 14. Dezember 2019, 22:45:57 CET schrieb Robert Krawitz:
> I'm seeing that somehow my index.xml has an item with id=0.  I'm not
> quite sure how it happened; I know I was using the preferences dialog
> to add a new member-group and then I created more member-groups under
> that.

I can see several categories with id="0" as well. Checking my index.xml 
backups it seems to be a long-standing issue: the first category with id=0 was 
introduced in my index.xml in May 2017. By itself, though that should not 
really be a problem (AFAICS id 0 is not handled specially compared to other 
index numbers).

What concerns me more though, is that categories with id=0 are duplicated. I 
see the first instance of a duplicate id in December 2017. It can't be 
triggered by routine operations, or I would expect to see far more duplicates.

So, two questions arise:
 - What is the cause for the bug?
 - How can we help users recover from this?

  Johannes