Fix error when creating root category
Fix error when creating root category

Tried to unindex/index with id='' which is obviously invalid

DirkHoffmann/indico,ThiefMaster/indico,indico/indico,mic4ael/indico,mvidalgarcia/indico,mic4ael/indico,mic4ael/indico,mvidalgarcia/indico,OmeGak/indico,mic4ael/indico,DirkHoffmann/indico,mvidalgarcia/indico,ThiefMaster/indico,ThiefMaster/indico,indico/indico,pferreir/indico,pferreir/indico,DirkHoffmann/indico,OmeGak/indico,indico/indico,ThiefMaster/indico,mvidalgarcia/indico,pferreir/indico,OmeGak/indico,DirkHoffmann/indico,pferreir/indico,indico/indico,OmeGak/indico