title: using vue.set in vuex is not updating the state
body: <p>I'm trying to add an object into a nested array, and it is not working, but I've used this for other states and it works fine.</p>
  
  <p>Has it got something to do with it begin a nested array?</p>
  
  <p>this is the code I'm using</p>
  
  <pre><code>Vue.set(state.sections[getCurrentSection(state).index].rows[getCurrentRow(state).index].columns[getCurrentColumn(state).index].elements, 0, element)
  </code></pre>
  
  <p>this is the element object </p>
  
  <pre><code>var element = {
      id: id,
      style: {
          backgroundColor: {
              value: 'rgba(255,255,255,1)',
          },
      },
  }
  </code></pre>
  
  <p>what am I doing wrong?</p>