title: Stringtemplate 4 (st4) - Render if string is not empty
body: <p>I need an st4 expression to render an element if a string is not empty:</p>
  
  <p><code>&lt;if(theString)&gt;...&lt;endif&gt;</code> does not work - it seems to only work for arrays.</p>
  
  <p>I've tried <code>if(theString.length &gt; 0)</code> and all kinds of stuff, but it looks like it this only works for variables that are not set or for arrays.</p>
  
  <p>I am iterating over a list and rendering this, so I could have values in the middle that are empty strings that I don't want to render anything at all for.</p>