Fixes button react component props

e2e/ScreenStyle.test.js

     await expect(elementByLabel(`Two`)).toExist();
   });
 
+  test(':ios: pass props to custom button component should exist after screen rerender', async () => {
+    await elementById(testIDs.PUSH_OPTIONS_BUTTON).tap();
+    await expect(elementByLabel(`Two`)).toExist();
+    await elementById(testIDs.SCROLLVIEW_SCREEN_BUTTON).tap();
+    await elementById(testIDs.POP_BUTTON).tap();
+    await expect(elementByLabel(`Two`)).toExist();
+  });
+
   test('tab bar items visibility', async () => {
     await elementById(testIDs.TAB_BASED_APP_BUTTON).tap();
     await expect(elementById(testIDs.FIRST_TAB_BAR_BUTTON)).toBeVisible();

lib/ios/RNNTopBarOptions.m

 		_navigationButtons = [[RNNNavigationButtons alloc] initWithViewController:(RNNRootViewController*)viewController];
 		[_navigationButtons applyLeftButtons:self.leftButtons rightButtons:self.rightButtons defaultLeftButtonStyle:self.leftButtonStyle defaultRightButtonStyle:self.rightButtonStyle];
 	}
+	
+	self.rightButtons = nil;
+	self.leftButtons = nil;
 }
 
 - (void)setRightButtonColor:(NSNumber *)rightButtonColor {
 		} else {
 			[_rightButtonStyle mergeWith:rightButtons];
 		}
+	} else {
+		_rightButtons = rightButtons;
 	}
 }
 
 		} else {
 			[_leftButtonStyle mergeWith:leftButtons];
 		}
+	} else {
+		_leftButtons = leftButtons;
 	}
 }
 

playground/src/screens/ScrollViewScreen.js

       topBarHideOnScroll: false
     };
     this.onClickToggleTopBarHideOnScroll = this.onClickToggleTopBarHideOnScroll.bind(this);
+    this.onClickPop = this.onClickPop.bind(this);
   }
 
   render() {
         <ScrollView testID={testIDs.SCROLLVIEW_ELEMENT} contentContainerStyle={styles.contentContainer}>
           <View>
             <Button title='Toggle Top Bar Hide On Scroll' testID={testIDs.TOGGLE_TOP_BAR_HIDE_ON_SCROLL} onPress={this.onClickToggleTopBarHideOnScroll} />
+            <Button title='Pop screen' testID={testIDs.POP_BUTTON} onPress={this.onClickPop} />
           </View>
         </ScrollView>
       </View>
     });
   }
 
+  onClickPop() {
+    Navigation.pop(this.props.componentId);
+  }
+
   componentDidUpdate() {
     Navigation.mergeOptions(this.props.componentId, {
       topBar: {