Fix issue with undefined action.

- Refactor overlay component.

src/renderer/component/overlay/view.jsx

@@ -9,7 +9,8 @@ type Props = {
 class Overlay extends React.PureComponent<Props> {
   render() {
     const { showOverlay, children } = this.props;
-    return <div className="overlay">{showOverlay ? children : ''}</div>;
+    if (!showOverlay) return '';
+    return <div className="overlay">{children}</div>;
   }
 }
 

src/renderer/redux/reducers/media.js

@@ -28,7 +28,7 @@ export default handleActions(
       paused: true,
     }),
 
-    [actions.MEDIA_POSITION]: (state: MediaState) => {
+    [actions.MEDIA_POSITION]: (state: MediaState, action: Action) => {
       const { outpoint, position } = action.data;
       return {
         ...state,