Set default StatusBarBackgroundColor in OptionsPresenter

This prevents the call to mergeOptions from applying statusBar color even
though it was not declared explicitly by the user.

lib/android/app/src/main/java/com/reactnativenavigation/parse/StatusBarOptions.java

@@ -1,6 +1,7 @@
 package com.reactnativenavigation.parse;
 
 import com.reactnativenavigation.parse.params.Color;
+import com.reactnativenavigation.parse.params.NullColor;
 import com.reactnativenavigation.parse.parsers.ColorParser;
 
 import org.json.JSONObject;
@@ -15,7 +16,7 @@ public class StatusBarOptions {
         return result;
     }
 
-    public Color backgroundColor = new Color(android.graphics.Color.BLACK);
+    public Color backgroundColor = new NullColor();
 
     public void mergeWith(StatusBarOptions other) {
         if (other.backgroundColor.hasValue()) backgroundColor = other.backgroundColor;

lib/android/app/src/main/java/com/reactnativenavigation/presentation/OptionsPresenter.java

@@ -1,6 +1,7 @@
 package com.reactnativenavigation.presentation;
 
 import android.app.Activity;
+import android.graphics.Color;
 import android.os.Build;
 import android.view.View;
 
@@ -39,7 +40,7 @@ public class OptionsPresenter {
 
     private void applyStatusBarOptions(StatusBarOptions statusBar) {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
-            activity.getWindow().setStatusBarColor(statusBar.backgroundColor.get());
+            activity.getWindow().setStatusBarColor(statusBar.backgroundColor.get(Color.BLACK));
         }
     }
 }