title: Confirmation URL for Shopify RecurringApplicationCharge is nil
body: <p>Im trying to add a recurring charge to my shopify app. I followed the <a href="https://shopify.dev/tutorials/add-billing-to-your-app" rel="nofollow noreferrer">Shopify-Tutorial</a> but wrote it slightly different. My root route goes to:</p>
  <pre><code>root 'mycontroller#charging'
  </code></pre>
  <p>the controller action is:</p>
  <pre><code>  def charging
      if @shop_domain != @myshop
        @shop_charging_status = @shop.charging
        unless ShopifyAPI::RecurringApplicationCharge.current
          recurring_charge = ShopifyAPI::RecurringApplicationCharge.new(
            name: &quot;My App&quot;,
            price: &quot;1.99&quot;,
            return_url: &quot;https:\/\/appurl\/activated&quot;,
            trial_days: 7,
            terms: &quot;$1.99 per month&quot;)
  
            if recurring_charge.save
              @tokens[:confirmation_url] = recurring_charge.confirmation_url
              @shop_charging_status = true
              @shop.save
              redirect recurring_charge.confirmation_url
            end
        end
      else
        redirect_to myindex_path
      end
  </code></pre>
  <p>When I try to start the app, i get an error: NoMethodError (undefined method `[]=' for nil:NilClass). It concerns the @token line. This line already confused me when i wrote the code, because the variable @token is only used in this method. But nevertheless, why is it nil?</p>
  <p>What am I missing?</p>