[FIX] Detailed view in Timetable show everything
[FIX] Detailed view in Timetable show everything

- The sessions without contributions are shown now.
- Closes task #739

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