Sorry about this, in my haste to copy and paste from the old addon, I missed an important part of code - yikes!
So this update fixes that (basically if you posted an article with no prefix at all it would fail)
As a bonus though and to say sorry about that, I've integrated another one of my addons into it.
Navigation Block Prefixes
If you enable this feature, the item assigned prefixes will appear in the navigation block, underneath the relevant category where the child categories...