1st modal flickers after closing 2nd children modal

Nobody has claimed this yet.

I got on one of my app screens, a button, that opens a modal, this modal has also a button, that shows a fullscreen modal. Whenever I close the latter, the first modal that is behind, flickers super fast that you can see for a millisecond the screen beneath and then it renders back again.

Is there any way to solve this issue? Haven't tested on Android, but i'm seeing this on iPhone X simulator iOS 12.1 and also on my iPhone 6S (device).

This is the way i'm setting up the 2nd modal which is full screen:

```
style={styles.modal}
backdrop={false}
isOpen={this.state.modalOpened}
onOpened={ () => this.setState({ modalOpened: true })}
onClosed={ () => this.setState({ modalOpened: false })}
position={'top'}
swipeToClose={false}
keyboardTopOffset={0}
coverScreen={true}
entry={'bottom'}
backdropPressToClose={false}>
```

RN info:
```
"react": "16.6.3",
"react-native": "0.57.8",
"react-native-modalbox": "^1.6.0",
```

Start by reproducing the nested modal close flow on iOS with the shown react-native-modalbox props, comparing the first modal with the screen beneath it. Read the modal open and close lifecycle in the package and verify that closing the fullscreen child no longer briefly reveals the underlying screen.

Written by the indexing model from the issue text.