title: Nlog - conditional layout based on message
body: <p>I want nlog to output newline when message is empty, when message is not empty, I want output layout.<br>
  I've tried following approach, but it doesn't work: </p>
  
  <pre><code>&lt;variable name="DefaultLayout" value="${time}  ${level:uppercase=true}: ${message}"/&gt;
  &lt;variable name="Main" value="${when:when='${message}'=='':inner=${newline}:else=${DefaultLayout}}"/&gt;
  ......
  &lt;target xsi:type="ColoredConsole" name="console" layout="${Main}" /&gt;
  </code></pre>
  
  <p>In this configuration it prints new line when message is empty, but when message is not empty, it doesn't print this message, only <code>16:06:34.7274  INFO</code><br>
  How to fix config to have desired effect? </p>