Fix template designer json validation
Fix template designer json validation

Validating the old data in the database doesn't make much sense and
may actually fail if e.g. some number is stored as a string in legacy
data.

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