title: Set default state value in ngrx reducer
body: <p>In store I have several array, string etc.</p>
  <pre><code>export const INITIAL_TEST_STORE: TestState = {
      one: null,
      two: null,
      three: false,
      four: {},
  };
  </code></pre>
  <p>And above, you can see initial state values - all are working properly.</p>
  <p>But when I dispatched clear action (and setting initial state):</p>
  <pre><code>on(clearState, state =&gt; ({
      ...INITIAL_TEST_STORE
  })),
  </code></pre>
  <p>the <code>four</code> node has still old value, not empty {}</p>
  <p>If I dispatch below action:</p>
  <pre><code>on(clearState, state =&gt; ({
      ...INITIAL_TEST_STORE,
      four: {}
  })),
      
  </code></pre>
  <p>Everything is clear properly. And I am wondering why? The problem is with immutable? But... it is that same...</p>