Fix duplicates on principalfield
Fix duplicates on principalfield

Fixes #2805

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