change validate_format to not validate formats if value is falsy
change validate_format to not validate formats if value is falsy

MeilleursAgents/validictory,fvieira/validictory,andrecp/validictory,ceymard/validictory,trigger-corp/validictory,brotchie/validictory,dokai/validictory,mgrandi/validictory,rhettg/validictory,andretw/validmore,alonho/validictory,talos/validictory,soulrebel/validictory,dmr/validictory,msabramo/validictory,stxnext/validictory,jalaziz/validictory,pombredanne/validictory,filod/validictory,Lujeni/validictory,enotodden/validictory,kyleconroy/validictory,sunlightlabs/validictory,ahassany/validictory,nicolaiarocci/validictory,travelbird/validictory