title: React-native, maps,The prop 'region.latitude' is marked as required in 'MapView' but it's value is null
body: <p>I'm getting this error when trying to get current location in Expo. I am getting the correct values at console.log though so I don't know what the problem is. In Expo it says 'Exception thrown while executing UI block, NSNull doublevalue: unrecognized selector sent to instance. Here's my code:</p>
  
  <pre><code>this.state = { text: 'Destination' ,
    latitude: null,
    longitude: null,
    error: null,
  
  componentDidMount() {
  navigator.geolocation.getCurrentPosition(
    (position) =&gt; {
      this.setState({
        latitude: position.coords.latitude,
        longitude: position.coords.longitude,
        error: null,
      });
    },
    (error) =&gt; this.setState({ error: error.message }),
    { enableHighAccuracy: true, timeout: 20000, maximumAge: 1000 },
  );
  
  {.....}
  render()
  &lt;MapView style={styles.map}
      region ={{
      latitude:this.state.latitude,
      longitude:this.state.longitude,
      latitudeDelta: 0.1,
      longitudeDelta: 0.1,
  </code></pre>