title: WP_Query->post_name returns null
body: <p>I'm trying to get the post_name attribute from <code>WP_Query($args)</code> function in wordpress. If I'm using <code>var_dump($wp_query);</code> it shows me that the <code>post_name</code> attribute is not empty or null. It is the title of the post.</p>
  
  <p>But if I'm trying to echo it using <code>echo $wp_query-&gt;post_name;</code> it returns an empty string.</p>
  
  <p>This is how I define <code>$wp_query</code>:</p>
  
  <pre><code>$args = array('posts_per_page' =&gt; 5, 'tag' =&gt; 'General');
  $wp_query = new WP_Query( $args );
  </code></pre>
  
  <p>There are some posts which has the tag "General" so this cannot be the reason.</p>
  
  <p>Can someone please explain that behaviour or tell me what I'm doing wrong?</p>