title: How do I return null in typescript
body: <p>In the following I need to return null in the case UserAction.LOGOUT_REQUESTED.  How an I do it or is there a better way to do it?</p>
  
  <pre><code>public static reducer(state: ILoginReducerState = UserReducer.initialState, action: ILogInAction): ILoginReducerState {
      switch (action.type) {
   case UserAction.LOGOUT_REQUESTED:
              return null}
  </code></pre>
  
  <p>The ILoginReducerState is defined as follows</p>
  
  <pre><code>export interface IlogIn
  { 
  userName : string,
  password:string,
  error:boolean
  }
  
  export interface ILoginReducerState 
  {
  readonly loading: boolean
  readonly currentUser: IlogIn
  readonly errors?: string
  }
  </code></pre>
  
  <p>Right now I am having the error [ts] Type 'null' is not assignable to type 'ILoginReducerState'.</p>
  
  <pre><code>private static readonly initialState: ILoginReducerState = {
      currentUser: {
          error:false,
          password:'',
          userName:'',
      },
      errors:'',
      loading: false,
  };
  </code></pre>