PR requetc changes

Author: Leo

FirebaseAdmin/FirebaseAdmin/Messaging/InstanceIdClient.cs

@@ -112,12 +112,6 @@ private async Task<TopicManagementResponse> SendInstanceIdRequest(string topic,
                 var json = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
                 this.errorHandler.ThrowIfError(response, json);
                 var instanceIdServiceResponse = JsonConvert.DeserializeObject<InstanceIdServiceResponse>(json);
-
-                if (instanceIdServiceResponse == null || instanceIdServiceResponse.ResultCount == 0)
-                {
-                    throw new ArgumentException("unexpected response from topic management service");
-                }
-
                 return new TopicManagementResponse(instanceIdServiceResponse);
             }
             catch (HttpRequestException e)
@@ -161,7 +155,7 @@ private void ValidateRegistrationTokenList(List<string> registrationTokens)
             {
                 if (string.IsNullOrEmpty(registrationToken))
                 {
-                    throw new ArgumentNullException("Registration tokens must not be null");
+                    throw new ArgumentException("Registration tokens must not be null or empty");
                 }
             }
         }

FirebaseAdmin/FirebaseAdmin/Messaging/InstanceIdServiceResponse.cs

@@ -29,7 +29,7 @@ internal class InstanceIdServiceResponse
         /// <summary>
         /// An instance Id response error.
         /// </summary>
-        public class InstanceIdServiceResponseElement
+        internal class InstanceIdServiceResponseElement
         {
             /// <summary>
             /// Gets a value indicating the error in this element of the response array. If this is empty this indicates success.