title: FirebaseMessaging is null null and SendMessage fails because of it
body: <p>I have a code here where I want to use FireBase Admin to send push notifications to IOS and Android. I recieve token, title and body from method.</p>
  <pre><code>var message = new FirebaseAdmin.Messaging.Message()
                  {
                      Notification = new FirebaseAdmin.Messaging.Notification
                      {
                          Title = title,
                          Body = body
                      },
                      Token = DeviceToken.First(),
                      Apns = new ApnsConfig { Aps = new Aps { ContentAvailable = true, Sound = &quot;default&quot;, Category = &quot;test&quot; } },
                      Android = new AndroidConfig { Notification = new AndroidNotification { ClickAction = &quot;test&quot; } }
                  };
  
                  var messaging = FirebaseMessaging.DefaultInstance;
  
                  await messaging.SendAsync(message);
  </code></pre>