title: How to know if block content is empty in Jade
body: <p>How can we check if block is exist in Jade, I'm trying to make a template in Jade where in i have following block in layout.jade and in login.jade i have extended layout.jade. Now when in account.jade i will have both left and main content blocks</p>
  
  <pre><code>extend layout.jade
     div(class='col-md-4')
        block leftcontainer
     div(class='col-md-8')
        block content
  </code></pre>
  
  <p>Now in login.jade i want to hide </p>
  
  <pre><code>   div(class='col-md-4')
         block leftcontainer
  </code></pre>
  
  <p>and make the main content full page, if leftcontainer is not there. It should look like this</p>
  
  <pre><code>  div(class='col-md-12')
       block content
  </code></pre>
  
  <p>if user is on some page i want to hide left column block. Say if user is in login page then</p>