Rails acts as tenant getting nil in model on Heroku

Im using gem 'acts_as_tenant' in a Rails 3 app.

I set the tenant in the applications controller based on domain:

  set_current_tenant_by_subdomain(:tenant, :subdomain)

I have code in the workorder model that needs to use the current_tenant:

class Workorder < ActiveRecord::Base
acts_as_tenant(:tenant)

if ActsAsTenant.current_tenant.data.present?
  ActsAsTenant.current_tenant.data.each do |key, value|
    ransacker key do |parent|
      Arel::Nodes::InfixOperation.new('->', parent.table[:data], key)
    end
  end
end

On my local Mac, this works fine. But, when I upload to Heroku, I get this error:

Sep 17 11:25:38 ndeavor-staging app/web.1:  /app/app/models/workorder.rb:8:in `<class:Workorder>': undefined method `data' for nil:NilClass (NoMethodError) 

So, ActsAsTenant.current_tenant is nil (on Heroku).

Why is that?

Thanks for the help!

UPDATE1

The same model uses ActsAsTenant.current_tenant in a where stmt with no problem:

  if ActsAsTenant.current_tenant.data != nil
    ActsAsTenant.current_tenant.data.each do |key, value|
      ransacker key do |parent|
        Arel::Nodes::InfixOperation.new('->', parent.table[:data], key)
      end
    end
  end

  def self.woclosed
    where("wostatus_id = ?", ActsAsTenant.current_tenant.workorder_closed).where(:archive => false)
  end

UPDATE2

I tried moving the code to the applications controller, but that doesn't even work locally:

class ApplicationController < ActionController::Base

set_current_tenant_by_subdomain(:tenant, :subdomain)

if current_tenant.data.present?
  current_tenant.data.each do |key, value|
    ransacker key do |parent|
      Arel::Nodes::InfixOperation.new('->', parent.table[:data], key)
    end
  end
end

But I get:

 NameError: undefined local variable or method `current_tenant' for ApplicationController:Class

UPDATE3

I tried another approach by looking up the Tenant based on the URL's subdomain. The lookup code works ok in a view, but it didn't in the model.

ct = Tenant.where(subdomain: request.subdomain).first
  if ct.data.present?
    ct.data.each do |key, value|
      ransacker key do |parent|
        Arel::Nodes::InfixOperation.new('->', parent.table[:data], key)
      end
    end
 end

I still don't know why ActsAsTenant.current_tenant is nil on Heroku.

But, the following fixed my issue:

class Workorder < ActiveRecord::Base
  acts_as_tenant(:tenant)

  ct = Tenant.find(self.first.tenant)
  if ct.data.present?
    ct.data.each do |key, value|
      ransacker key do |parent|
        Arel::Nodes::InfixOperation.new('->', parent.table[:data], key)
      end
    end
  end