Fix validator when linked field is empty
Fix validator when linked field is empty

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