RB: Fix NULL field on rollback (location)
RB: Fix NULL field on rollback (location)

Room creation was crashing because accessing `.attributes.all()` forced a rollback.

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