Can't set background color to be transparent.

### Version
- react-native-router-flux v4.2.0
- react v16.11.0
- react-native v0.62.2

Can anyone help me find what I am missing? I have been stuck on this issue for the last little while and feel like I have explored every avenue.

### Expected behaviour

Router output renders transparently over the background image.

### Actual behaviour

The router output has a white background.

### Reproducible Demo
Here is my root App.tsx
```tsx
const App: () => React$Node = () => {

return (
<>



















);
};
```
and here is my FluxRouter component.
```tsx
export const FluxRouter = () => {
return (
















)
}

const sceneStyle = () => {
let style = {
backgroundColor: 'transparent'
}
return style;
}

```