title: Why firebase return true even with empty input
body: <p>Basically the program should checks for the existance of the data in the Firebase database based on the input and display the pop up accordingly, but if I left the input as empty, somehow it still considered the data does exists by prompting the 'Request' pop-out window.  </p>
  
  <pre><code>@Override
  public void onClick(View v) {
  
    final String input = mInput.getText().toString();
  
    DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
    DatabaseReference idRef = rootRef.child("Patient");
    idRef.addListenerForSingleValueEvent(new ValueEventListener() {
  
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
  
        if (dataSnapshot.child(input).getValue() != null) {
            startActivity(new Intent(addNew.this, Request.class));
        } else{
            startActivity(new Intent(addNew.this, Fail.class));
        }
    }
  
        @Override
        public void onCancelled(DatabaseError databaseError) {}
     });
  }
  </code></pre>
  
  <p>I would like to know how to solve it so that the empty Input considered as inexistence data, thanks for the help</p>