title: NLog logs Error twice in same file
body: <p>I am trying to figure out why NLog logs my error twice.</p>
  
  <p>here is my config file:</p>
  
  <pre><code>&lt;nlog xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"&gt;
    &lt;targets&gt;
      &lt;target name="debug" xsi:type="File" FileName="DebugTestFile.log" layout="${message} ${exception:format=tostring}" /&gt;
    &lt;/targets&gt;
    &lt;rules&gt;
      &lt;logger name="*" level="Debug" writeTo="debug" /&gt;
    &lt;/rules&gt;
  &lt;/nlog&gt;
  </code></pre>
  
  <p>Now when I call <code>NLog.Debug(myException);</code> the output is my exception gets printed twice.</p>
  
  <p>If I call <code>NLog.Debug(myException, "My Test Message String");</code> then the error gets printed out once along with my test message.</p>
  
  <p>What exactly am I doing wrong?  According to <a href="https://github.com/NLog/NLog/wiki/How-to-Log-Exceptions" rel="noreferrer">https://github.com/NLog/NLog/wiki/How-to-Log-Exceptions</a> my configuration is correct.</p>
  
  <p>I tried changing my layout to the following: <code>layout="${message}</code> and when I ran <code>NLog.Debug(myException);</code> it only printed the error once.  </p>
  
  <p>However now when I ran <code>NLog.Debug(myException, "My Test Message String");</code> it only printed my message without the error that comes from exception.</p>
  
  <p>Could this be a bug with NLog?</p>