[FIX] Session default duration for contribution
[FIX] Session default duration for contribution

- Closes #1328

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