问Heroku only错误:在Heroku上的Rails中未定义方法`write_from_user‘，但在dev中一切正常

EN

2016-11-01T05:20:15.948227+00:00 app[web.1]: [7a7a60bf-b9bf-404d-890e-3692ba99bad0] Completed 500 Internal Server Error in 12ms (ActiveRecord: 2.8ms)
2016-11-01T05:20:15.949267+00:00 app[web.1]: [7a7a60bf-b9bf-404d-890e-3692ba99bad0]   
2016-11-01T05:20:15.949316+00:00 app[web.1]: [7a7a60bf-b9bf-404d-890e-3692ba99bad0] NoMethodError (undefined method `write_from_user' for nil:NilClass):
2016-11-01T05:20:15.949353+00:00 app[web.1]: [7a7a60bf-b9bf-404d-890e-3692ba99bad0]   
2016-11-01T05:20:15.949490+00:00 app[web.1]: [7a7a60bf-b9bf-404d-890e-3692ba99bad0] app/controllers/gdrs_controller.rb:12:in `create'

def create
  @des = Designer.where(email: Rails.application.secrets.design_lead_email)
  @gdr = Gdr.new(secure_params)
  @gdr[:uuid] = SecureRandom.hex(5)
  @gdr.designer = @des
  @gdr[:status] = "Queued"
  if @gdr.save!
    VisitorMailer.gdr_created_email(@gdr).deliver_now
    DesignerMailer.gdr_created_email(@gdr).deliver_now
    redirect_to gdr_url(@gdr[:uuid])
  else
    render :new
  end
end

private

def secure_params
    params.require(:gdr).permit(:uuid, :client_name, :email, :dept, :ext, :cost_centre, :activity_type, :project_name, :description, :size, :quantity, :colour, :quote, :rush, :rush_desc, :proof_date, :print_date, :delivery_instructions, :reprint, :old_gl, :server_path_to_files, :activity_code) 
end