Fix email validation on user creation
Fix email validation on user creation

Make sure the email field isn't empty in the first place instead of
returning 500 afterwards.

alkadis/vcv,SysTheron/adhocracy,SysTheron/adhocracy,phihag/adhocracy,SysTheron/adhocracy,alkadis/vcv,DanielNeugebauer/adhocracy,phihag/adhocracy,alkadis/vcv,alkadis/vcv,liqd/adhocracy,alkadis/vcv,liqd/adhocracy,phihag/adhocracy,DanielNeugebauer/adhocracy,phihag/adhocracy,liqd/adhocracy,DanielNeugebauer/adhocracy,DanielNeugebauer/adhocracy,liqd/adhocracy,DanielNeugebauer/adhocracy,phihag/adhocracy