[FIX] ParameterManager handling integers
[FIX] ParameterManager handling integers

It now handles empty int fields and allows default value for them

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