diff --git a/example/lib/src/rtm_api_demo.dart b/example/lib/src/rtm_api_demo.dart
index 21c827d..3456c86 100644
--- a/example/lib/src/rtm_api_demo.dart
+++ b/example/lib/src/rtm_api_demo.dart
@@ -160,7 +160,7 @@ class _RtmApiDemoState extends State<RtmApiDemo> {
                   await RTM(config.appId, _userIdController.text);
               if (status.error) {
                 logSink.log(
-                    '[error] operation: ${status.operation}, reason: ${status.reason}');
+                    '[error] errorCode: ${status.errorCode}, operation: ${status.operation}, reason: ${status.reason}');
                 return;
               }
               _rtmClient = client;
@@ -264,11 +264,9 @@ class _RtmApiDemoState extends State<RtmApiDemo> {
                 _button('RtmClient.unsubscribe', () async {
                   final (status, result) =
                       await _rtmClient.unsubscribe(_channelNameController.text);
-                  if (status.error) {
-                    return;
-                  }
+
                   logSink.log(
-                      '[UnsubscribeResult] channelName: ${result!.channelName}, errorCode: ${status.errorCode}');
+                      '[UnsubscribeResult] channelName: ${result?.channelName}, errorCode: ${status.errorCode}');
                 }),
               ],
             ),
@@ -312,12 +310,9 @@ class _RtmApiDemoState extends State<RtmApiDemo> {
                     recordUserId: _isSetChannelMetadataRecordUserId,
                     lockName: _setChannelMetadataLockNameController.text,
                   );
-                  if (status.error) {
-                    return;
-                  }
 
                   logSink.log(
-                      '[SetChannelMetadataResult] channelName: ${result!.channelName}, channelType: ${result.channelType}, errorCode: ${status.errorCode}');
+                      '[SetChannelMetadataResult] channelName: ${result?.channelName}, channelType: ${result?.channelType}, errorCode: ${status.errorCode}');
                 }),
                 _button('RtmStorage.updateChannelMetadata', () async {
                   final storage = _rtmClient.getStorage();
@@ -339,12 +334,8 @@ class _RtmApiDemoState extends State<RtmApiDemo> {
                     lockName: _setChannelMetadataLockNameController.text,
                   );
 
-                  if (status.error) {
-                    return;
-                  }
-
                   logSink.log(
-                      '[UpdateChannelMetadataResult] channelName: ${result!.channelName}, channelType: ${result.channelType}, errorCode: ${status.errorCode}');
+                      '[UpdateChannelMetadataResult] channelName: ${result?.channelName}, channelType: ${result?.channelType}, errorCode: ${status.errorCode}');
                 }),
                 _button('RtmStorage.removeChannelMetadata', () async {
                   final storage = _rtmClient.getStorage();
@@ -360,23 +351,17 @@ class _RtmApiDemoState extends State<RtmApiDemo> {
                         .toList(),
                     lockName: _setChannelMetadataLockNameController.text,
                   );
-                  if (status.error) {
-                    return;
-                  }
 
                   logSink.log(
-                      '[RemoveChannelMetadataResult] channelName: ${result!.channelName}, channelType: ${result.channelType}, errorCode: ${status.errorCode}');
+                      '[RemoveChannelMetadataResult] channelName: ${result?.channelName}, channelType: ${result?.channelType}, errorCode: ${status.errorCode}');
                 }),
                 _button('RtmStorage.getChannelMetadata', () async {
                   final storage = _rtmClient.getStorage();
                   final (status, result) = await storage.getChannelMetadata(
                       _channelNameController.text, _rtmChannelType);
-                  if (status.error) {
-                    return;
-                  }
 
                   logSink.log(
-                      '[GetChannelMetadataResult] channelName: ${result!.channelName}, channelType: ${result.channelType}, data: ${result.data.toJson()} errorCode: ${status.errorCode}');
+                      '[GetChannelMetadataResult] channelName: ${result?.channelName}, channelType: ${result?.channelType}, data: ${result?.data.toJson()} errorCode: ${status.errorCode}');
                 }),
               ],
             ),
@@ -406,12 +391,9 @@ class _RtmApiDemoState extends State<RtmApiDemo> {
                     includeUserId: _isWhoNowIncludeUserId,
                     page: _isWhoNowPageController.text,
                   );
-                  if (status.error) {
-                    return;
-                  }
 
                   logSink.log(
-                      '[WhoNowResult] userStateList: [${result!.userStateList.map((e) => e.toJson())}], nextPage: ${result.nextPage}, errorCode: ${status.errorCode}');
+                      '[WhoNowResult] userStateList: [${(result?.userStateList ?? []).map((e) => e.toJson())}], nextPage: ${result?.nextPage}, errorCode: ${status.errorCode}');
                 }),
               ],
             ),