lastMessage doesn't have the text message parameter

Sendbird Chat API/SDK Flutter
1

After the change in FeedChannel by the replace of lastMessage data type from BaseMessage to NotificationMessage there is no possibility to get the text message. I’ve checked the parameters the closest one would be ‘data’ but the value is empty. On iOS this is working , but i assume because it implements BaseMessage.

[SDK Version]
// What version of the SDK are you using?
v4.2.9

[Reproduction Steps]
// Please provide reproduction steps and, if possible, code snippets.

 FeedChannel.getChannel(feed_url).then((channel) {
          setState(() {
            lastMessage = channel.lastMessage.data;  // string is empty, doesn't have any other param
          });
        });

[Frequency]
// How frequently is this issue occurring?
always
[Current impact]
// How is this currently impacting your implementation?
Can get lastMessage text string