[KPhotoAlbum] Crash when renaming categories (and possible fix)

[Tobias Leupold]

Hi list!

I found a crash situation in current git master. You can produce it like so:

* Open the "Categories" settings page
* Rename a category
* Click "Apply"
* Rename it again
* Click "Apply" again

--> KPA crashes.

I think this is due to _categoryOrig in CategoryItem.cpp not being set to the 
current (updated) category name, but still pointing to the original name (it 
is overwritten by the submit function).

I'm not perfectly sure if this is okay and works fine. It's only a tiny 
change, but with this, the crash does not occur anymore and all renaming seems 
still to be working:
https://github.com/l3u/kphotoalbum/compare/fix_rename_crash

Could you please review this?

Yours, Tobias