In my debugging I saw that index.row() was giving -1. I found that this was coming from the missing X-SuSE-YaST-Group entry in one of the .desktop files which is used for grouping the entries. When no group entry is found, this method gets ultimately called with an index pointing at the (invalid) row -1. I suppose index.row() returns something signed, so the check there is not enough, as it doesn't work for -1.