Added missing output case for T_NULL in json_writer
Added missing output case for T_NULL in json_writer

BrewPi/firmware,etk29321/firmware,glibersat/firmware,etk29321/firmware,BrewPi/firmware,BrewPi/firmware,glibersat/firmware,glibersat/firmware,BrewPi/firmware,etk29321/firmware,BrewPi/firmware,glibersat/firmware,BrewPi/firmware,BrewPi/firmware,BrewPi/firmware,etk29321/firmware,etk29321/firmware,glibersat/firmware,glibersat/firmware,glibersat/firmware,etk29321/firmware