title: Why im getting this error Warning: Operand of null-aware operation '??' has type 'String' which excludes null. Dart Language
body: <p>so i was learning about SWITCH and CASE Statements in dart language, in the course he explains the code but he don't get an error while i get one.</p>
  <p>the error i get
  : Warning: Operand of null-aware operation '??' has type 'String' which excludes null.
  String ``userName = name ?? &quot;Guest User&quot;;</p>
  <p>My Code is</p>
  <pre><code>void learnCondExpr() {
   String name = 'Yamix';
      
   String userName = name ?? &quot;Guest User&quot;;
   print(userName);
  }
  </code></pre>
  <p>can i get some help please :)</p>