title: No margin / padding bottom on css grid?
body: <p>margin bottom seems to disappear on css grid when overflow appears.</p>
  
  <p>no matter which way i approach the layout of my page (flexbox, css grid, fixed) i seem to loose margin/padding bottom when using css grid.</p>
  
  <p>an example of the issue:</p>
  
  <p>HTML</p>
  
  <pre><code>&lt;div class="header"&gt;&amp;nbsp;&lt;/div&gt;
  &lt;div class="nav"&gt;&amp;nbsp;&lt;/div&gt;
  &lt;div class="article"&gt;
         &lt;div class="settings__grid"&gt;
          &lt;div class="settings__grid-item"&gt;&amp;nbsp;&lt;/div&gt;
          &lt;div class="settings__grid-item"&gt;&amp;nbsp;&lt;/div&gt;
          &lt;div class="settings__grid-item"&gt;&amp;nbsp;&lt;/div&gt;
          &lt;div class="settings__grid-item"&gt;&amp;nbsp;&lt;/div&gt;
          &lt;div class="settings__grid-item"&gt;&amp;nbsp;&lt;/div&gt;
          &lt;div class="settings__grid-item"&gt;&amp;nbsp;&lt;/div&gt;
        &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>CSS</p>
  
  <pre><code>html,
  body {
    margin: 0;
    height: 100%;
  }
  .header {
    position: fixed;
    z-index: 2;
    top: 0;
    left: 0;
    width: 100%;
    height: 20px;
    background: white;
    box-shadow: 0px 2px 4px rgba(0, 0, 0, 0.24);
  }
  .nav {
    position: fixed;
    z-index: 1;
    top: 20px;
    left: 0;
    width: 200px;
    height: calc(100% - 20px);
    background: #FAF9F8;
    border-right: 1px solid #d9d9d9;
  }
  
  .article {
    background: #F3F3F5;
    position: relative;
    top: 20px;
    left: 200px;
    width: calc(100% - 200px);
    height: calc(100% - 20px);
    padding: 10px;
  }
  
  .settings__grid {
    display: grid;
    height: 100%;
  
    grid-template-columns: repeat(auto-fit, minmax(32rem, 1fr));
    grid-auto-rows: 14rem;
    grid-gap: 3rem;
  }
  
  .settings__grid-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: space-evenly;
    text-align: center;
    background-color: rgba(0, 0, 0, 0.4);
    border-radius: 6px;
  }
  
  @media (max-width: 768px) {
    .nav {
      bottom: 0;
      left: 0;
      right: 0;
      top: auto;
      width: 100%;
      height: 60px;
    }
    .article {
      height: calc(100% - 80px);
      left: 0;
      width: 100%;
    }
  }
  </code></pre>
  
  <p><a href="https://codepen.io/anon/pen/EzWmeg" rel="noreferrer">https://codepen.io/anon/pen/EzWmeg</a></p>
  
  <p>i expect the margin/padding to be consistent to what i define on parent but it doesn't and disappears / collapses</p>