Update when topSpacing prop is changed

Andr3wHur5t#56
A fix for Andr3wHur5t#49. I tried to avoid manually writing a componentWillReceiveProps function to keep the code simpler.

KeyboardSpacer.js

@@ -105,7 +105,7 @@ export default class KeyboardSpacer extends Component {
     // when external physical keyboard is connected
     // event.endCoordinates.height still equals virtual keyboard height
     // however only the keyboard toolbar is showing if there should be one
-    const keyboardSpace = (screenHeight - event.endCoordinates.screenY) + this.props.topSpacing;
+    const keyboardSpace = screenHeight - event.endCoordinates.screenY;
     this.setState({
       keyboardSpace,
       isKeyboardOpened: true
@@ -135,6 +135,17 @@ export default class KeyboardSpacer extends Component {
 
   render() {
     return (
-      <View style={[styles.container, { height: this.state.keyboardSpace }, this.props.style]} />);
+      <View
+        style={[
+          styles.container,
+          {
+            height:
+              this.state.keyboardSpace +
+              (this.state.isKeyboardOpened ? this.props.topSpacing : 0)
+          },
+          this.props.style
+        ]}
+      />
+    );
   }
 }