ruby - Getting error when validating picture presence Rails 4 -

this gig model

class gig < activerecord::base   has_attached_file :image, :styles => { :medium => "360x170>", :bigger => "650x459>" }   validates_attachment_content_type :image, :content_type => /\aimage\/.*\z/   validate :image_size_validation    def image_size_validation     if image.size > 2.megabytes       errors.add(:base, "image should less 2mb")     end   end end 

everything works great,i can not upload picture greater 2mb wanted,and gives notice that(written me).

question: when save form(of new product),without selecting picture,it throws error saying undefined method > nil:nilclass. instead of saying user,that should upload picture,so form can saved.

gig controller create

def create     @gig = current_user.gigs.build(gig_params)      if @gig.save       redirect_to @gig, notice: "gig created"     else       render "new"     end   end 

that error thrown line:

if image.size > 2.megabytes 

obviously, if there isn't image... won't have size.

how check nil there:

def image_size_validation   return if image.blank?   if image.size > 2.megabytes