a better task handling

ZicMoove/ZicMoove.Droid/OAuth2/YaOAuth2Authenticator.cs

@@ -380,6 +380,8 @@ public class YaOAuth2Authenticator : WebRedirectAuthenticator
             }
 
             var auth = req.GetResponseAsync().ContinueWith(task =>
+            {
+                if (task.IsCompleted)
                 {
                     var text = task.Result.GetResponseText();
                     req.Abort();
@@ -398,6 +400,15 @@ public class YaOAuth2Authenticator : WebRedirectAuthenticator
                     {
                         throw new AuthException("Expected access_token in access token response, but did not receive one.");
                     }
+                }
+                else if (task.IsFaulted)
+                {
+                    throw new AuthException("Unexpected fault");
+                }
+                else
+                {
+                    throw new AuthException($"Ended: {task.Status}");
+                }
             });