Fix crash when unmounting WrappedComponent

[wsxyeah]

Check if has routeName to prevent crash

[mcabs3]

Do you have an example of what would cause this crash?

[wsxyeah]

@mcabs3 Yes.

Add a key for the container in Example.js (just like the LightBox).
Then choose the RN menu Toggle Inspector on the device, you will see the crash.

<Router>
  <Modal>
    <LightBox key="lightbox_top"> // here
      <Stack key="root"/>
      // other scenes …
    </LightBox>
  </Modal>
</Router>

[wsxyeah]

@mcabs3 Oh, I found the root cause now.

Sine the OverlayNavigator passed wrong state to its child overlay components, the children will never get this.props.navigation.state.routeName.

[mcabs3]

@wsxyeah so is this change irrelevant now?