title: Detect firebase child value is "null" or "0"
body: <p><a href="https://i.stack.imgur.com/jimif.png" rel="nofollow noreferrer">This is the value in inside my firebaseDatabse</a></p>
  
  <p><a href="https://i.stack.imgur.com/BBHop.png" rel="nofollow noreferrer">This is how I retrieve user infomation (e.g Name &amp; Age)</a></p>
  
  <p>My questions is how to I check if the child value is "null"? 
  Help and guidance needed...... 
  Thanks</p>