Fix scrolled content being visible behind navigation view group

app/src/main/res/layout/navigation_view_group.xml

@@ -4,6 +4,7 @@
     android:layout_width="match_parent"
     android:layout_height="?attr/listPreferredItemHeightSmall"
     android:gravity="center_vertical"
+    android:background="?android:attr/colorBackground"
     android:orientation="horizontal"
     android:paddingStart="?attr/listPreferredItemPaddingStart"
     android:paddingEnd="?attr/listPreferredItemPaddingEnd">