title: displayName showing null after creating user with Firebase Auth
body: <p>I'm trying to add a user using the Firebase auth and it returns the displayName as null, even though it asks for it via the UI on sign up.  Any ideas why and how to fix?  Here's the code I am using to do this:</p>
  
  <pre><code>startActivityForResult( AuthUI.getInstance()
                                              .createSignInIntentBuilder()
                                              .setProviders(Collections.singletonList(new AuthUI.IdpConfig.Builder(AuthUI.EMAIL_PROVIDER).build()))
                                              .build(), RC_SIGN_IN);
  </code></pre>
  
  <p>and in the Activity for Result....</p>
  
  <pre><code>protected void onActivityResult(int requestCode, int resultCode, Intent data) {
      super.onActivityResult(requestCode, resultCode, data);
      if (resultCode == RESULT_OK) {
          // user is signed in!
  
          //save user
          saveUser();
  
          startMainActivity();
          return;
      }
  </code></pre>
  
  <p>save user code is as follows:</p>
  
  <pre><code>private void saveUser(){
      FirebaseUser fUser = FirebaseAuth.getInstance().getCurrentUser();
      final User user = new User();
      if (fUser.getDisplayName() != null) {
          user.setUserName(fUser.getDisplayName());
      } else {
          Log.e("FB_info", "User has no display name");
      }
      user.setUserEmail(fUser.getEmail());
  
      final DatabaseReference userRef =         FirebaseDatabase.getInstance().getReference(FirebaseRefs.getUsersRef()).child(fUser.getUid());
      userRef.addListenerForSingleValueEvent(new ValueEventListener() {
          @Override
          public void onDataChange(DataSnapshot dataSnapshot) {
              if(!dataSnapshot.exists()){
                  userRef.updateChildren(user.toMap());
              }
          }
  
          @Override
          public void onCancelled(DatabaseError databaseError) {
  
          }
      });
  
  }
  </code></pre>
  
  <p>Any idea why the display name is returning null?</p>