title: Shorter Alternative to ternary to generate empty string if nil?
body: <p>I have a parameter of Type <code>Double?</code>.
  When this parameter is <code>nil</code>, I want to have an empty string.</p>
  <p>I can use <code>if (variable == nil) ? &quot;&quot; : String(variable!)</code> but is there a shorter alternative?</p>