title: Type mismatch: inferred type is String? but String was expected
body: <p>Due to this line in my codes : </p>
  
  <pre><code>var myRef = child_myRef.child(FirebaseAuth.getInstance().uid) 
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/qZajO.png" alt="Type mismatch: inferred type is String? but String was expecte"></p>