Tab Navigation + Different Tab Stack Lengths

Hi,
I'm trying to use this wonderful library to implement the Android Back Button functionality mentioned in [this blog article](https://medium.com/the-many/handling-android-back-button-events-in-react-native-with-custom-components-b33c63b0633b).

Problem is, my use case is a little different, it can't automatically use the "last mounted" component I use for catching the back button event, it needs to use the one of the currently focused screen.

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For example, this works:
1. `Tab A`: `Tab A Root`
2. `Tab B`: `Tab B Root` > `Screen B` <- focused, back button here, listener of Screen B called correcty
3. `Tab C`: `Tab C Root`

While this is not working:
1. `Tab A`: `Tab A Root`
2. `Tab B`: `Tab B Root` > `Screen B` <-- focused, back button here, **listener of Subscreen C is called**
3. `Tab C`: `Tab C Root`> `Screen C` > `Subscreen C`

Any ideas how this scenario could be handled? Thanks!