Sample category page with a block design for sections

category_page.hbs

<div class="container-divider"></div>
<div class="container">
  <nav class="sub-nav">
    {{breadcrumbs}}
    {{search submit=false scoped=true}}
  </nav>

  <div class="category-container">
    <div class="category-content">
      <header>
        <h1>{{category.name}}</h1>
      </header>

      <section class="categories blocks">
        <ul class="blocks-list">
          
            {{#each sections}}
            <li class="blocks-item">
                  <a href='{{url}}' class="blocks-item-link">
                    <h4 class="blocks-item-title">{{name}}</h4>
                    <p class="blocks-item-description">{{excerpt description}}</p>
                  </a>
                  {{#if internal}}
                    <span class="icon-lock" title="{{t 'internal'}}"></span>
                  {{/if}}
            </li>
            {{/each}}
        </ul>
    		</section>
    </div>
  </div>
</div>

'internal' does not exist. What to do? And where to insert the code in category_page.hbs?