title: Add menu page is creating submenu with same title name
body: <p>I am using this function to create  menu option in wp dashboard</p>
  
  <pre><code>       add_menu_page(
      __('Advertisement Pages'),// the page title
      __('Advertisement'),//menu title
      'edit_themes',//capability 
      'a-advertise',//menu slug/handle this is what you need!!!
      'display_all_ad',//callback function
      '',//icon_url,
      '15'//position
  );
  </code></pre>
  
  <p>it is creating menu the name of Advertisement but also creating submenu with the same name.</p>