title: one2many in kanban nothing is displayed
body: <p>I am using Odoo 12. I don't have access to Odoo's Python part, only the Odoo developer mode. I installed the <code>web_one2many_kanban</code> module but apart from the images and the id of the lines of my <code>one2many</code>, I can not display the rest of the data.</p>
  
  <p>My code:</p>
  
  <pre><code>&lt;t t-name="kanban-box"&gt;
    &lt;div t-attf-class="oe_kanban_card  {{ record.x_bom_line_ids.raw_value }}"&gt;
      &lt;t t-if="record.x_bom_line_ids.raw_value"&gt;
        &lt;div class="row"&gt;
          &lt;div class="col-8"&gt;
            &lt;strong&gt;
              &lt;span&gt;
                &lt;t t-esc="record.product_id.value"/&gt;
              &lt;/span&gt;
            &lt;/strong&gt;
          &lt;/div&gt;
          &lt;div class="col-4"&gt;
            &lt;strong&gt;
              &lt;span class="float-right text-right"&gt;
                &lt;t t-esc="record.x_virtual_available.value"/&gt;
              &lt;/span&gt;
            &lt;/strong&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      &lt;/t&gt;
    &lt;/div&gt;
  &lt;/t&gt;
  
  &lt;t t-foreach="record.x_bom_line_ids.raw_value" t-as="room"&gt;
    &lt;img t-att-src="kanban_image('mrp.bom.line', 'x_image', room)" t-att-data-member_id="room" /&gt;
  </code></pre>
  
  <p>My error:</p>
  
  <pre><code>"Uncaught TypeError: Cannot read property 'value' of undefined"
  </code></pre>