title: Doxygen generates empty pages
body: <p>I have a page in markdown format with subpages inside.</p>
  
  <pre><code>page.md
  |
  |_\subpage page1 Page1
  |_\subpage page2
  </code></pre>
  
  <p>inside page1.md</p>
  
  <pre><code>\page page1 PAGE1
    content
  </code></pre>
  
  <p>but when I generate the html output, it creates in the tree view, a empty page1 without content in the main branch of the tree. and another page1 in the correct place with content in the treeview.</p>
  
  <p>How can I get rid of this empty page?</p>