Dynamically populate a submenu with posts

gistfile1.php

<?php
/**
 * Adds the most recent "Some Category" posts as sub menu items under
 * the "Some Category Parent" parent menu item.
 * 
 * @param array $items
 * @param array $menu
 * @param array $args
 * @return array
 */
function ja_dynamic_submenu( $items, $menu, $args ) {

	// Only proceed if we are looking at the correct menu and not in the admin
	if ( $menu->slug != 'primary-navigation' || is_admin() )
		return $items;

	// Placeholders
	$new_menu_items = array();
	$menu_id        = '';

	// Find the menu item we are looking for, with the title "Some Category Parent"
	foreach ( $items as $item ) {
		if ( 'Some Category Parent' == $item->title )
			$menu_id = $item->ID;
	}

	// Create the query for the posts to list
	$menu_args = array (
		'posts_per_page' => 4,
		'category_name'  => 'some-category',
	);									
	$menu = new WP_Query( $menu_args ); while( $menu->have_posts() ) : $menu->the_post();
		$new_menu_items[] = array(
			'title' => get_the_title(),
			'url'   => get_permalink(),
		);
	endwhile;

	$menu_order = count( $items ) + 1;

	// Add the new menu items
	if ( !empty( $new_menu_items ) && !empty( $menu_id ) ) {
		foreach ( $new_menu_items as $new_menu_item ) {
			$new_item = new stdClass;
			$new_item->menu_item_parent = $menu_id;
			$new_item->url = $new_menu_item['url'];
			$new_item->title = $new_menu_item['title'];
			$new_item->menu_order = $menu_order;
			$items[] = $new_item;
			$menu_order++;
		}		
	}

	wp_reset_postdata();
	wp_reset_query();

	return $items;
}
add_filter( 'wp_get_nav_menu_items', 'ja_dynamic_submenu', 10, 3 );

$new_item = new stdClass;

caused the following errors for me.

Notice: Undefined property: stdClass::$object_id in C:\Apache\htdocs\wordpress\wp-includes\nav-menu-template.php on line 518

Notice: Undefined property: stdClass::$db_id in C:\Apache\htdocs\wordpress\wp-includes\nav-menu-template.php on line 626

To fix the problem, i replaced the code on line 44 with:

$_post = new stdClass;
$new_item = new WP_Post($_post);

Wow, It works very well. Thanks for code @jaredatch and thanks @moyarich for code correction suggestions.