Stop returning null when visible changes (#84)

Returning null wipes out the modal component, if the state changes too quickly this causes the modal to get stuck on the screen even between reloads. Better to let the modal handles its own visibility change.

Author: kimihiro64

index.js

@@ -136,8 +136,6 @@ export default class Spinner extends React.PureComponent {
   }
 
   _renderSpinner() {
-    if (!this.state.visible) return null;
-
     const spinner = (
       <View
         style={[styles.container, { backgroundColor: this.props.overlayColor }]}