Cannot set navigationBarStyle when using navTransparent=true

### Version
Tell us which versions you are using:

- react-native-router-flux v4.2.0
- react v16.13.1
- react-native v0.63.4

### Expected behaviour

Should be able to set navigationBarStyle when using navTransparent=true

### Actual behaviour

When setting navTransparent=true, navigationBarStyle is omitted, I think this is the line:

https://github.com/aksonov/react-native-router-flux/blob/b9377e3b39752cf19fa9f7d2c530543efd0be3db/src/Store.js#L331

### Steps to reproduce
For non-obvious bugs, please fork this component, modify Example project to reproduce your issue and include link here.
1. In the demo, set navTransparent=true and navigationBarStyle={{ paddingTop: 24 }}
2. Run the project
3. paddingTop is omitted