title: Wordpress: the_content filter kills gallery shortcode
body: <p>My the_content filter kills gallery shortcode and I dont know where the problem is...
  I can add just blank the_content filter and gallery disappear from the content and there is just <code>[gallery]</code> text. I am using the_content filter:</p>
  
  <pre><code>function test($data){
      echo $data;
  }
  add_filter('the_content', 'test');
  </code></pre>
  
  <p>Any suggestion how to fix it?</p>