title: Update root fields in a redux store property
body: <p>I'm having trouble updating only a couple of fields in my redux state (<code>shopListDisplayed</code>, and <code>rerenderKey</code>). By the way I'm using an immutable js record for the state. </p>
  
  <p>State:</p>
  
  <p><a href="https://i.stack.imgur.com/eb2Q7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eb2Q7.png" alt="enter image description here"></a></p>
  
  <p>I want to update <code>addPage.shopListDisplayed</code>. I'm not sure if it is possible with this data shape. The code enters into the below reducer with the correct action, and correct boolean value, but the state does not update. </p>
  
  <pre><code>    export function createReducer(initialState, handlers) {
        return function reducer(state = initialState, action) {
          if (handlers.hasOwnProperty(action.type)) {
            return handlers[action.type](state, action)
          } else {
            return state
          }
        }
      }
  
      export const addPageReducer: Reducer&lt;AddPageAction&gt; = createReducer(
        applicationState.get('addPage') , {
          UPDATE_SHOP_LIST_DISPLAYED : updateShopListDisplayed
      })
  
  
      const updateShopListDisplayed = (state: ProductPage, action): ProductPage =&gt; {
        return state.set('shopListDisplayed', (action.payload: boolean))
      }
  
  
  const rootReducer = combineReducers({
    addPage: combineReducers({
      shopInputControl: shopInputControlReducer, 
      product: productReducer,
      page: addPageReducer
    }),
    search: combineReducers({
      location: combineReducers({ autocomplete, location })
    }),
    alertModal,
    categories,
    editProduct,
    map,
    menu,
    searchResults,
    searchResultsPresenter
  })
  </code></pre>
  
  <p>Is it possible to update these two fields in my redux store?</p>